Mobility-modifying cyanine dyes

ABSTRACT

The present invention provides a novel class of fluorescent cyanine dye compounds that are modified at one of the hetercyclic ring nitrogen atoms with a mobility-modifying moiety that permits the electrophoretic mobilities of polynucleotides labeled with the mobility-modifying cyanine dyes to be adjusted or tuned in a predictable fashion while retaining enzymatic activity. The ability to predictably tune the relative electrophoretic mobilities of the dyes permits the creation of sets of mobility-matched fluorescent dyes of a variety of structures for a variety of applications, including fluorescence-based 4-color nucleic acid sequencing reactions.

1. CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.09/477,270, filed Jan. 4, 2000 which is incorporated herein byreference.

2. FIELD OF THE INVENTION

The present invention relates generally to fluorescent dye compoundsthat are useful as molecular probes. In particular, the presentinvention relates to fluorescent cyanine dye compounds that are mobilitymodified for use in nucleic acid sequencing reactions.

3. BACKGROUND OF THE INVENTION

The advent of automated four-color Sanger-type DNA sequencing hasrevolutionized the speed with which stretches of DNA can be reliablysequenced. In four-color Sanger-type DNA sequencing, a single-strandedtarget DNA of interest is hybridized with a complementary primer and theprimer enzymatically extended with a DNA polymerase in the presence of amixture of 2′-deoxyribonucleotides capable of supporting continuousprimer extension (e.g., dATP, dGTP, dCTP and dTTP or dUTP) and a mixtureof four labeled terminators. Each of the terminators is labeled with adifferent, spectrally distinguishable fluorescent label and terminatesprimer extension at a single type of template nucleotide. A mixture ofterminators is used such that a termination event is achieved at eachtype of template nucleotide. The product of this primer extension orsequencing reaction is a nested set of labeled primer extension productsin which the 3′-terminal nucleotide is identifiable by the color of itsfluorescent label. These products are then electrophoreticallyseparated, typically in a single gel lane or capillary, and the sequenceof the target DNA determined from the colors of the resultantelectrophoresis bands.

To avoid ambiguities in determining the sequence of the target DNA, thedyes used to label the primer extension products should either impart noelectrophoretic mobility shifts on the products or impart uniformmobility shifts. However, in most instances, different types of dyesimpart vastly different electrophoretic mobility shifts. Since the dyesmust be spectrally distinguishable from one another, dyes havingdifferent structures, and hence quite different imparted electrophoreticmobility shifts, must be used. While sets of terminators that impartprimer extension products with similar mobility shifts are available,rationally designing such sets of “mobility matched” terminators iscurrently virtually impossible. Rather, the sets are obtained throughempirical trial and error. To date, no methods exists whereby one canpredictably alter the electrophoretic mobilities imparted by terminatorslabeled with desirable dyes without altering the spectral properties ofthe dyes and/or jeopardizing the abilities of the labeled terminators toact as substrates for polymerizing enzymes. Accordingly, these areobjects of the present invention.

4. SUMMARY OF THE INVENTION

These and other objects are furnished by the present invention, which inone aspect provides cyanine dye compounds having a mobility-modifyingmoiety that permits the electrophoretic mobilities of polynucleotideslabeled with the dyes to be adjusted or tuned in a predictable fashion.

Cyanine dyes are a well-recognized class of fluorescent molecules whichgenerally comprise first and second parent heteroaromatic ring systemscovalently linked together via a methine, polymethine or cyclic alkylenebridge. The dyes may be homodimers, in which the first and second parentheteroaromatic ring systems are both members of the same class, or theymay be heterodimers, in which the first and second parent heteroaromaticring systems are both members of different classes. The parent ringsystems may be optionally substituted with one or more substituentswhich can serve to alter the spectral, chemical and/or physicalproperties of the dyes.

The present invention concerns the class of cyanine dyes in which bothparent heteroaromatic rings belong to the class of rings generallyreferred to as benzazoles/benzazoliums. The mobility-modifying cyaninedyes of the invention generally comprise: (i) a first parentbenzazole/benzazolium heteroaromatic ring system that is substituted atthe heteroaromatic ring nitrogen with a linking moiety; (ii) a secondparent benzazole/benzazolium heteroaromatic ring system that issubstituted at the heteroaromatic ring nitrogen with amobility-modifying moiety; and (iii) a bridge linking the first andsecond parent benzazole/benzazolium rings via their respective C-2carbons. The first and second parent benzazole/benzazolium ring systemsmay be the same or different, and may be optionally substituted with oneor more of the same or different substituent groups. Preferably, bothparent benzazole/benzazolium ring systems are the same or differentsubstituted or unsubstituted indoline/indolinium ring systems. Dependingupon the particular application, the linking moiety can be used toconjugate, preferably by way of covalent attachment, themobility-modifying dyes of the invention to other molecules orsubstances.

Quite significantly, since the mobility-modified and linking moietiesare located at opposing ends of the cyanine dye (i.e., on differentheteroaromatic rings), nucleosides/tides and/or nucleoside/tide analogslabeled with the mobility-modifying cyanine dyes of the invention, e.g.,labeled 2′-deoxyribonucleoside-5′-triphosphates and labeled terminatingribonucleoside-5′-triphosphates (e.g.,2′,3′-dideoxyribonucleoside-5′-triphosphates), retain high activity assubstrates for DNA polymerizing enzymes, making the mobility-modifyingdyes ideal for use in fluorescence-based nucleic acid sequencingapplications. Moreover, since the: electrophoretic mobilities ofpolynucleotides labeled with the mobility-modifying dyes can bepredictably tuned to match those labeled with other dyes, themobility-modifying dyes of the invention are ideal for use in 4-colorfluorescence-based nucleic acid sequencing reactions, as sets of dyeshaving matched mobilities in addition to desirable spectral andbiological properties can be readily obtained.

Virtually any known cyanine dye can be mobility-modified according tothe principles of the invention. Thus, parent heteroaromatic ringsystems of which the dyes of the invention can be comprised include, butare not limited to, the substituted and unsubstitutedbenzazole/benzazolium rings comprising the cyanine, merocyanine andstyryl dyes described in U.S. Pat. Nos. 5,486,616, 5,569,587, 5,569,766and 5,627,027; the substituted and unsubstituted benzazole/benzazoliumrings comprising the asymmetric cyanine dyes described in U.S. Pat. Nos.5,321,130, 5,410,030, 5,436,134, 5,534,416, 5,582,977, 5,658,751,5,656,449, and 5,863,753; and the substituted and unsubstitutedbenzazole/benzazolium rings comprising the various sulfonated cyaninedyes described in Tu et al., 1998, Nucl. Acids Res. 26(11):2797-2802,the disclosures of which are incorporated herein by reference.Additional substituted and unsubstituted benzazole/benzazolium ringsystems of which the mobility-modifying cyanine dyes may be comprisedare described in Brooker et al., 1945, “Absorption Spectra of Dyes withHeteroaromatic Nuclei—Color and Constitution. Part VII. Intepretation ofAbsorptions of Dyes Containing Heterocyclic Nuclei of DifferentBasicities,” J. Am. Chem. Soc. 67:1875-1889 (in particular at page1878), the disclosure of which is incorporated herein by reference.

The mobility-modifying moiety comprises a pendant group bearing aplurality of charges through substitution with one or more of the sameor different charged substituents. The pendant group can be any moietycapable of being substituted with the desired number of chargedsubstituents, but is typically a group having the structure -D-D′, whereD is (C₁-C₆) alkyldiyl or 2-6 membered heteroalkyldiyl; and D′ is(C₁-C₆) alkyl, 2-6 membered heteroalkyl, (C₅-C₁₄) aryl, (C₅-C₁₄)arylaryl, 5-14 membered heteroaryl or 5-14 memberedheteroaryl-heteroaryl. When D is heteroalkyldiyl, it must be attached tothe benzazole/benzazolium ring nitrogen atom via an alkyldiyl group.Preferred amongst the various D groups is (C₁-C₆) alkyleno, particularly(C₁-C₆) alkanos such as methano (—CH₂—), ethano (—CH₂—CH₂—), propano(—CH₂—CH₂—CH₂—), etc.

The polarity of the charged substituents substituting the pendant groupdepends upon the direction of the desired electrophoretic mobilityshift. When an increase in electrophoretic mobility is desired, anionicsubstitutents should be used. When a decrease in electrophoreticmobility is desired, cationic substiutents should be used. When multiplecharged substitutents are used they can be the same or different, andcan even be of mixed polarities, although in most instances all of thecharged substituents will have the same polarity.

The number of charged substituents substituting the pendant groupdepends upon the desired net charge of the mobility-modifying moiety,which in turn depends upon the identity of the charged substituent andthe degree of mobility modification necessary. The charged substituentsmay be any substituent group having a net charge at the desired pH ofuse (typically pH 6 to 10). Suitable cationic substituents include, byway of example and not limitation, permanent cations such as quaternaryammoniums, especially those of the formula —N⁺RRR, where each R isindependently (C₁-C₆) alkyl, and cations derived from bases. Permanentcations or cationic substituents that are derived from strong bases(“strong cationic substituents”), such as those having a pK_(a) of about8 or greater, are preferred, as these strong cationic substituents arecompletely ionized at the pHs commonly employed in biological assayssuch as nucleic acid sequencing reactions.

Suitable anionic substituents include groups having a pK_(a) of 6 orless, and include by way of example and not limitation, —C(O)O⁻,—P(O)(O⁻)₂, —P(O)(OH)(O⁻), —O—P(O)₂(O⁻), —S(O)₂O⁻ and —O—S(O)₂O⁻(including any associated counterions). Anionic substituents that arederived from strong acids (“strong anionic substituents”), such as thosehaving a pK_(a) of 3 or less, are preferred, as these strong anionicsubstituents are completely ionized at the pHs commonly employed inbiological assays such as nucleic acid sequencing reactions. Preferredamongst the strong anionic substituents are —S(O)₂O⁻ and —O—S(O)₂O⁻.

In addition to the desired charged substituents, the pendant group maybe further substituted with one or more additional unchargedsubstituents. Such uncharged substituents can serve a variety ofpurposes, e.g., to increase the water solubility of themobility-modifying dye, to decrease non-specific binding of themobility-modifying dyes and/or to decrease the interactions betweenchromophores of multiply labeled compounds, thereby decreasing quenchingof fluorescence.

The bridge joining the two parent heteroaromatic ring systems can be anytype of bridge commonly used to join the parent heteroaromatic ringsystems of cyanine dyes. Preferably, the bridge permits electrondelocalization. Electron-delocalizing bridges useful for linking theheteroaromatic rings of the dyes include, but are not limited to,methine, polymethine, squarine and cyclic alkene bridges. The bridgesmay be optionally substituted with one or more of the same or differentsubstituents that typically serve to increase the chemical and/orphotostability of the dye and/or increase its quantum yield.

The linking moiety has the structure -L-LG, where L is a linker and LGis a linking group that can be used to conjugate, preferably by way ofcovalent attachment, the mobility-modifying cyanine dye to anothercompound or substance, such as a protein, nucleoside/tide,polynucleotide, polymer, particle etc. The identity of linking group LGwill depend upon the nature of the desired conjugation. For example, theconjugation may be: (i) mediated by ionic interactions, in which caselinking group LG is a charged group; (ii) mediated by hydrophobicinteractions, in which case linking group LG is a hydrophobic moiety;(iii) mediated by covalent attachment, in which case linking group LG isa reactive functional group (R_(x)) that is either capable of forming acovalent linkage with another complementary functional group (F_(x)) oris capable of being activated so as to form a covalent linkage withcomplementary functional group F_(x); or (iv) mediated through the useof pairs of specific binding molecules, such as biotin andavidin/streptavidin, in which case linking group LG is one member of thepair, e.g., biotin.

The linking group LG is attached to the benzazole/benzazolium ringnitrogen via linker L. Depending upon the application, linker L can behydrophobic, hydrophilic, long or short and/or rigid, semirigid orflexible. Regardless of the identity of the linker L, in order to avoidadversely affecting the spectral properties of the cyanine dyechromophore, it must be attached to the benzazole/benzazolium nitrogenatom via an alkyldiyl group.

In another aspect, the invention provides labeled conjugates comprisinga mobility-modifying cyanine dye according to the invention and anothermolecule or substance. The mobility-modifying cyanine dye is conjugatedto the other molecule or substance, typically via covalent attachment,through linking group LG as previously described. Once conjugated, thedye provides a convenient fluorescent label for subsequent detection.The dyes of the invention can be used to fluorescently label a widevariety of molecules and substances, including amino acids, proteins,antibodies, enzymes, receptors, nucleosides/tides, nucleic acids,carbohydrates, lipids, steroids, hormones, vitamins, drugs, metabolites,toxins, organic polymers, etc. The dyes can also be used to labelparticles such as nanoparticles, microspheres or liposomes. The moleculeor substance may be labeled with one or more mobility-modifying cyaninedyes of the invention, which may be the same or different.

In one preferred embodiment, the labeled conjugate is a labelednucleoside/tide or nucleoside/tide analog. The dye may be conjugated toeither the sugar or nucleobase moiety of the receptive nucleoside/tideor nucleoside/tide analog, but is usually conjugated to the nucleobasemoiety.

The labeled nucleoside/tide or nucleoside/tide analog may beenzymatically incorporable, in which case it may be conveniently used inconjunction with a template nucleic acid, a primer and appropriatepolymerizing enzymes to enzymatically generate labeled polynucleotides.A particularly preferred class of enzymatically-incorporable labelednucleoside/tides and nucleoside/tide analogs are labeled terminators, assuch terminators can be conveniently used in Sanger-type sequencingreactions to generate labeled polynucleotide sequencing fragments havingdefined gel electrophoretic mobilities.

Alternatively, the labeled nucleoside/tide or nucleoside/tide analog maybe synthetically incorporable, such as a labeled nucleosidic ornon-nucleosidic phosphoramidite synthesis reagent. Such reagents can beconveniently used in conjunction with standard solid phaseoligonucleotide synthesis reagents and supports to label syntheticpolynucleotides and/or polynucleotide analogs at their 3′-terminus,their 5′-terminus and/or at one or more internal positions withmobility-modifying dyes of the invention.

In another aspect, the invention provides methods of using the dyes ofthe invention to sequence a target nucleic acid. The method generallycomprises forming a series of differently-sized primer extensionproducts that are labeled with a dye of the invention, separating theseries of differently-sized labeled extension products, typically basedon size, and detecting the separated labeled extension products based onthe fluorescence of the label. The sequence of the target nucleic acidis then assembled according to known techniques.

The series of differently-sized labeled extension products can beconveniently generated by enzymatically extending a primer-target hybridaccording to well-known methods. For example, the series of labeledextension products can be obtained using a primer labeled with a dye ordye pair of the invention and enzymatically extending the labeledprimer-target hybrid in the presence of a polymerase, a mixture ofenzymatically-extendable nucleotides or nucleotide analogs capable ofsupporting continuous primer extension and at least one, typicallyunlabeled, terminator that terminates primer extension uponincorporation (e.g., a 2′,3′-dideoxyribonucleoside-5′-triphosphate).Alternatively, the series of labeled extension products can be obtainedusing an unlabeled primer and enzymatically extending the unlabeledprimer-target hybrid in the presence of a polymerase, a mixture ofenzymatically-extendable nucleotides or nucleotide analogs capable ofsupporting continuous primer extension and at least one terminatorlabeled with a dye of the invention. In either embodiment, thepolymerase serves to extend the primer with enzymatically-extendablenucleotides or nucleotide analogs until a terminator is incorporated,which terminates the extension reaction. Once terminated, the series oflabeled extension products are separated, typically based on size, andthe separated labeled extension products detected based on thefluorescence of the labels. The sequence of the target is then obtainedvia conventional means.

In a particularly advantageous embodiment of this method, a mixture offour different terminators are used in a single extension reaction. Eachdifferent terminator is capable of terminating primer extension at adifferent template nucleotide, e.g., a mixture of 7-deaza-ddATP, ddCTP,7-deaza-ddGTP and ddTTP or ddUTP, and is labeled with a different,spectrally-resolvable fluorophore, where at least one of thefluorophores is a mobility-modifying dye according to the invention.According to this embodiment, an unlabeled primer-target nucleic acidhybrid is enzymatically extended in the presence of, a polymerase, amixture of enzymatically-extendable nucleotides or nucleotide analogscapable of supporting continuous primer extension and a mixture of thefour different, labeled terminators. Following separation based on size,a series of separated labeled extension products is obtained in whichthe emission properties (i.e., color) of each separated extensionproduct reveals the identity of its 3′-terminal nucleotide. In aparticularly preferred embodiment, all of the labeled terminators areexcitable using a single light source.

Alternatively, terminators may be used in the absence ofenzymatically-extendable nucleotides. In this instance, the primer isextended by only a single base. Again, the primer may be labeled or,alternatively, one or more of the terminators may be labeled.Preferably, a mixture of four different labeled terminators is used, asdescribed above. These “mini sequencing” embodiments are particularlyuseful for identifying polymorphisms in chromosomal DNA or cDNA.

In yet another aspect, the invention provides mobility-matched sets oflabeled terminators and/or polynucleotide primers that can beconveniently used in Sanger-type sequencing reactions to generatesequencing ladders having matched electrophoretic mobilities. For4-color nucleic acid sequencing applications, one or severalconventional cyanine dyes having the desired spectral properties can beselected and the respective comparative mobilities of polynucleotidefragments labeled therewith obtained. The cyanine dyes can then besimply mobility-modified according to the principles taught herein totune the electrophoretic mobilities of polynucleotides labeled therewithas necessary to obtain sets of dyes that are mobility-matched. Apreferred set of mobility-matched terminators includes Compounds 31, 32,33 and 34 (see Section 5.10, infra). A preferred set of mobility-matchedpolynucleotide primers includes primers labeled with the dyechromophores of Compounds 31, 32, 33 and 34.

In a final aspect, the invention provides kits comprising themobility-modifying cyanine dyes and/or labeled conjugates of theinvention and reagents useful for labeling molecules and/or forperforming assays such as nucleic acid sequencing.

The mobility-modifying cyanine dyes of the invention provide significantadvantages over currently available cyanine dyes. Because themobility-modifying moiety does not significantly alter the spectralproperties of the cyanine dye chromophore, these dyes are useful invirtually any applications that utilize fluorescent dyes. However, owingto their ability to predictably alter the electrophoretic mobilities ofpolynucleotides labeled therewith, the mobility-modifying dyes of theinvention provide the ability to create mobility-matched sets offluorescent dyes for applications involving the electrophoreticseparation of labeled polynucleotides, such as automated nucleic acidsequencing. In particular, mixed dye sets (i.e., dyes with differentstructures) may be conveniently employed in automated sequencingapplications due to the ability to match the respective mobilities ofpolynucleotides labeled therewith according to this invention. Moreover,enzymatically-incorporable nucleoside/tides, enzymatically-incorporablenucleoside/tide analogs and terminators labeled with themobility-modifying dyes of the invention retain high enzymatic activitywith the polymerases commonly employed in automated nucleic acidsequencing methods, including thermostable polymerases such as AMPLITAQ®DNA polymerase FS (PE Biosystems, Foster City, Calif.).

5. DETAILED DESCRIPTION OF THE INVENTION

5.1 Abbreviations

The abbreviations used throughout the specification to refer to certainnucleobases, nucleosides and/or nucleotides are those commonly employedin the art and are as indicated below:

Expression Abbreviation

-   -   adenine A    -   7-deazaadenine 7-deaza-A    -   N⁶-Δ²-isopentenyladenine 6iA    -   N⁶-Δ²-isopentenyl-2-methylthioadenine 2 ms6iA    -   cytosine C    -   guanine G    -   6-thioguanine 6sG    -   7-deazaguanine 7-deaza-G    -   N²-dimethylguanine 2dmG    -   7-methylguanine 7mG    -   thymine T    -   4-thiothymine 4sT    -   uracil U    -   dihydrouracil D

Expression Abbreviation

-   -   4-thiouracil 4sU    -   base Y Y    -   ribonucleoside-5′-triphosphate NTP    -   adenosine-5′-triphosphate ATP    -   7-deazaadenosine-5′-triphosphate 7-deaza-ATP    -   cytidine-5′-triphosphate CTP    -   guanosine-5′-triphosphate GTP    -   7-deazaguanosine-5′-triphosphate 7-deaza-GTP    -   thymidine-5′-triphosphate TTP    -   uridine-5′-triphosphate UTP    -   2′-deoxyribonucleoside-5′-triphosphate dNTP    -   2′-deoxyadenosine-5′-triphosphate dATP    -   2′-deoxy-7-deazaadenosine-5′-triphosphate 7-deaza-dATP    -   2′-deoxycytidine-5′-triphosphate dCTP    -   2′-deoxyguanosine-5′-triphosphate dGTP    -   2′-deoxy-7-deazaguanosine-5′-triphosphate 7-deaza-dGTP    -   2′-deoxythymidine-5′-triphospate dTTP    -   2′-deoxyuridine-5′-triphosphate dUTP    -   2′,3′-dideoxyribonucleoside-5′-triphosphate ddNTP    -   2′,3′-dideoxyadenosine-5′-triphosphate ddATP    -   2′,3′-dideoxy-7-deazaadenosine-5′-triphosphate 7-deaza-ddATP    -   2′,3′-dideoxycytidine-5′-triphosphate ddCTP    -   2′,3′-dideoxyguanosine-5′-triphosphate ddGTP    -   2′,3′-dideoxy-7-deazaguanosine-5′-triphosphate 7-deaza-ddGTP    -   2′,3′-dideoxythymidine-5′-triphosphate ddTTP    -   2′,3′-dideoxyuridine-5′-triphosphate ddUTP

5.2 Definitions

As used herein, the following terms are intended to have the followingmeanings:

“Spectrally Resolvable:” means, in reference to a set of fluorescentdyes, that the fluorescence emission bands of the respective dyes aresufficiently distinct, i.e., sufficiently non-overlapping, that thedyes, either alone or when conjugated to other molecules or substances,are distinguishable from one another on the basis of their fluorescencesignals using standard photodetection systems such as photodetectorsemploying a series of band pass filters and photomultiplier tubes,charged-coupled devices (CCD), spectrographs, etc., as exemplified bythe systems described in U.S. Pat. Nos. 4,230,558 and 4,811,218 or inWheeless et al., 1985, Flow Cytometry: Instrumentation and DataAnalysis, pp. 21-76, Academic Press, New York. Preferably, all of thedyes comprising a spectrally resolvable set of dyes are excitable by asingle light source.

“Mobility-Matched:” refers to a set of fluorescent dyes that, when usedto label polynucleotides of equal lengths with one dye molecule per eachpolynucleotide molecule, yields differentially labeled polynucleotideshaving substantially similar electrophoretic mobilities. Typically, therelative electrophoretic mobilities of the labeled polynucleotides willvary by less than about one-half nucleotide. Preferably, themobility-matched dyes are spectrally resolvable, as previously defined.

“Mobility-modifying Dye Chromophore:” refers to a mobility-modifyingcyanine dye according to the invention exclusive of its linking moiety-L-LG. For example, the mobility-modifying dye chromophore derived fromthe mobility-modifying dye according to structural formula (I.A) has thestructure:

-   -   wherein k, l, m, Z, Z′, R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R¹¹, R¹² R³,        R¹⁴, R¹⁹, R²⁰ R²¹, R²² and MM are as defined for structural        formula (I.A), infra, and the dotted line protruding from the        heteroaromatic ring nitrogen represents the site of attachment        of the linking moiety -L-LG. Mobility-modifying dye chomophores        can be derived from other structural formulae described herein        in a similar manner.

“Nucleobase:” refers to a substituted or unsubstitutednitrogen-containing parent heteroaromatic ring of a type that iscommonly found in nucleic acids. Typically, but not necessarily, thenucleobase is capable of forming Watson-Crick and/or Hoogsteen hydrogenbonds with an appropriately complementary nucleobase. Exemplarynucleobases include, but are not limited to, purines such as2-aminopurine, 2,6-diaminopurine, adenine (A), ethenoadenine,N⁶-Δ²-isopentenyladenine (6iA), N⁶-Δ²-isopentenyl-2-methylthioadenine (2ms6iA), N⁶-methyladenine, guanine (G), isoguanine, N²-dimethylguanine(dmG), 7-methylguanine (7mG), 2-thiopyrimidine, 6-thioguanine (6sG)hypoxanthine and O⁶-methylguanine; 7-deaza-purines such as7-deazaadenine (7-deaza-A) and 7-deazaguanine (7-deaza-G); pyrimidinessuch as cytosine (C), 5-propynylcytosine, isocytosine, thymine (T),4-thiothymine (4sT), 5,6-dihydrothymine, O⁴-methylthymine, uracil (U),4-thiouracil (4sU) and 5,6-dihydrouracil (dihydrouracil; D); indolessuch as nitroindole and 4-methylindole; pyrroles such as nitropyrrole;nebularine; base (Y); etc. Additional exemplary nucleobases can be foundin Fasman, 1989, Practical Handbook of Biochemistry and MolecularBiology, pp. 385-394, CRC Press, Boca Raton, Fla., and the referencescited therein. Preferred nucleobases are purines, 7-deazapurines andpyrimidines. Particularly preferred nucleobases are the normalnucleobases, defined infra, and their common analogs, e.g., 2 ms6iA,6iA, 7-deaza-A, D, 2dmG, 7-deaza-G, 7mG, hypoxanthine, 4sT, 4sU and Y.

“Normal Nucleobase:” refers to a nucleobase that is naturally-occurringand encoding, i.e., adenine, cytosine, guanine, thymine or uracil.

“Nucleoside:” refers to a compound consisting of a nucleobase covalentlylinked, typically via a heteroaromatic ring nitrogen, to the C1′ carbonof a pentose sugar. Typical pentose sugars include, but are not limitedto, those pentoses in which one or more of the carbon atoms are eachindependently substituted with one or more of the same or different —R,—OR, —NRR or halogen groups, where each R is independently hydrogen,(C₁-C₆) alkyl or (C₅-C₁₄) aryl. The pentose sugar may be saturated orunsaturated. Exemplary pentose sugars include, but are not limited to,ribose, 2′-deoxyribose, 2′-(C₁-C₆)alkoxyribose,2′-(C₅-C₁₄)aryloxyribose, 2′,3′-dideoxyribose, 2′,3′-didehydroribose,2′-deoxy-3′-haloribose, 2′-deoxy-3′-fluororibose,2′-deoxy-3′-chlororibose, 2′-deoxy-3′-aminoribose,2′-deoxy-3′-(C₁-C₆)alkylribose, 2′-deoxy-3′-(C₁-C₆)alkoxyribose,2′-deoxy-3′-(C₅-C₁₄)aryloxyribose, 2′,3′-dideoxy-3′-haloribose and2′,3′-dideoxy-3′-fluororibose.

When the nucleobase is a purine or a 7-deazapurine, the pentose sugar isattached to the N9 or C8 position of the nucleobase. When the nucleobaseis a pyrimidine, the pentose sugar is attached to the N1-position of thenucleobase (see, e.g., Kornberg and Baker, 1992, DNA Replication, 2^(nd)Ed., Freeman, San Francisco), except for pseudouridines, in which thepentose sugar is attached to the C5 position of the uracil nucleobase.Preferred nucleosides are those in which the nucleobase is a purine, a7-deazapurine, a pyrimidine, a normal nucleobase or a common analog of anormal nucleobase and the pentose sugar is any of the exemplary pentosesugars listed above.

“Normal Nucleoside:” refers to a compound consisting of a normalnucleobase covalently linked via the N1 (C, T or U) or N9 (A or G)position of the nucleobase to the C1′ carbon of ribose or2′-deoxyribose.

“Nucleoside Analog:” refers to a nucleoside in which the pentose sugaris replaced with a pentose sugar analog. Exemplary pentose sugar analogsinclude, but are not limited to, substituted or unsubstituted furanoseshaving more or fewer than 5 ring atoms, e.g., erythroses and hexoses andsubstituted or unsubstituted 3-6 carbon acyclic sugars. One or more ofthe carbon atoms may be independently substituted with one or more ofthe same or different —R, —OR, —NRR or halogen groups, where each R isindependently hydrogen, (C₁-C₆) alkyl or (C₅-C₁₄) aryl.

“Nucleotide:” refers to a nucleoside in which one or more, typicallyone, of the pentose carbons is substituted with a phosphate ester havingthe formula:

-   -   where α is an integer from 0 to 4. Preferably, α is 2 and the        phosphate ester is attached to the 3′- or 5′-carbon of the        pentose. Particularly preferred nucleotides are those in which        the nucleobase is a purine, a 7-deazapurine, a pyrimidine, a        normal nucleobase or a common analog thereof.

“Normal Nucleotide:” refers to a normal nucleoside in which the 3′- or5′-carbon of the ribose or 2′-deoxyribose is substituted with aphosphate ester having the formula:

-   -   where α is an integer from 0 to 2. Preferred normal nucleotides        are those in which a is 2 and the phosphate ester is attached to        the 5′-carbon of the ribose (NTP) or 2′-deoxyribose (dNTP).    -   “Nucleotide Analog:” refers to a nucleotide in which the pentose        sugar and/or one or more of the phosphate esters is replaced        with its respective analog. Exemplary pentose sugar analogs are        those previously described in conjunction with nucleoside        analogs. Exemplary phosphate ester analogs include, but are not        limited to, alkylphosphonates, methylphosphonates,        phosphoramidates, phosphotriesters, phosphorothioates,        phosphorodithioates, phosphoroselenoates, phosphorodiselenoates,        phosphoroanilothioates, phosphoroanilidates, phosphoroamidates,        boronophosphates, etc., including any associated counterions, if        present.

Also included within the defintion of “nucleotide analog” are nucleobasemonomers which can be polymerized into polynucleotide analogs in whichthe DNA/RNA phosphate ester and/or sugar phosphate ester backbone isreplaced with a different type of linkage.

“Enzymatically-Incorporable Nucleotide or Nucleotide Analog:” refers toa nucleotide or nucleotide analog which is capable of acting as asubstrate for a polymerizing enzyme in a template-directed nucleic acidsynthesis reaction such that it is enzymatically incorporated into anascent polynucleotide or polynucleotide analog chain. Typicalenzymatically-incorporable nucleotides and nucleotide analogs are thosein which the sugar is a pentose. Preferred enzymatically-incorporablenucleotides are those in which the nucleobase is a purine, a7-deazapurine, a pyrimidine, a normal nucleobase or a common analogthereof and the pentose is a pentose-5′-triphosphate, such as NTPs,dNTPs and ddNTPs.

“Enzymatically-Extendable Nucleotide or Nucleotide Analog:” refers to anenzymatically-incorporable nucleotide or nucleotide analog that, onceincorporated into a nascent polynucleotide or polynucleotide analogchain, supports incorporation of further nucleotides or nucleotideanalogs. Thus, enzymatically-extendable nucleotides or nucleotideanalogs have a hydroxyl group that is capable of forming a covalentlinkage with another, subsequent nucleotide or nucleotide analog.Typical enzymatically-extendable nucleotides and nucleotide analogs arethose in which the sugar is a pentose. Preferredenzymatically-extendable nucleotides are those in which the nucleobaseis a purine, a 7-deazapurine, a pyrimidine, a normal nucleobase or acommon analog thereof and the pentose sugar is a3′-hydroxylpentose-5′-triphosphate, such as NTPs and dNTPs.

“Terminator:” refers to an enzymatically-incorporable nucleotide ornucleotide analog which does not support incorporation of subsequentnucleotides or nucleotide analogs. Typical terminators are those inwhich the nucleobase is a purine, a 7-deaza-purine, a pyrimidine, anormal nucleobase or a common analog thereof and the sugar moiety is apentose which includes a 3′-substituent that blocks further synthesis.Substituents that block further synthesis include, but are not limitedto, amino, deoxy, halogen, alkoxy and aryloxy groups. Exemplaryterminators include, but are not limited to, those in which thesugar-phosphate ester moiety is 2′,3′-dideoxyribose-5′-triphosphate,2′,3′-dideoxy-3″-aminoribose-5′-triphosphate,2′-3′-dideoxy-3″-haloribose-5′-triphosphate,2′,3′-dideoxy-3″-fluororibose-5′-triphosphate,2′-deoxy-3′-(C₁-C₆)alkoxyribose-5′-triphosphate,2′-deoxy-3′-(C₅-C₁₄)aryloxyribose-5′-triphosphate,2′,3′-dideoxy-3″-(C₁-C₆)alkylribose-5′-triphosphate and2′,3′-didehydroribose-5′-triphosphate.

“Nucleoside/tide:” refers to a nucleoside and/or a nucleotide and/or amixture thereof.

“Polynucleotide:” refers to a linear polymeric chain of nucleosidemonomer units that are covalently connected to one another by phosphateester internucleoside linkages. Unless stated otherwise,“polynucleotide” as used herein includes polymers of any length,including oligonucleotides, polynucleotides and nucleic acids as thoseterms are commonly used in the art. Where polynucleotides of specificsize ranges are intended, the number of monomer units is specificallydelineated. Thus, polynucleotides according to the invention can rangein size from a few monomer units (e.g., 4 to 40), to several hundreds ofmonomer units, to several thousands of monomer units, or even moremonomer units. Whenever a polynucleotide is represented by a sequence ofletters, e.g. “ATGCCTG,” it will be understood that the sequence ispresented in the 5′→3′ direction. 2′-Deoxyribopolynucleotides arepreceded with the letter “d,” e.g. “d(ATGCCTG).”

Polynucleotides may be composed of a single type of sugar moiety, as inthe case of RNA and DNA, or mixtures of different sugar moieties, as inthe case of RNA/DNA chimeras. Preferred polynucleotides areribopolynucleotides and 2′-deoxyribopolynucleotides according to thestructural formulae below:

-   -   wherein:        -   each B is independently a nucleobase, preferably a purine, a            7-deazapurine, a pyrimidine, a normal nucleobase or a common            analog thereof;        -   each m defines the length of the respective polynucleotide            and can range from zero to thousands, tens of thousands, or            even more;        -   each R is independently selected from the group consisting            of hydrogen, halogen, fluoro, (C₁-C₈) alkyl, —OR″ and            —NR″R″, where each R″ is independently hydrogen, (C₁-C₆)            alkyl or (C₅-C₁₄) aryl, or two adjacent Rs are taken            together to form a bond such that the ribose sugar is            2′,3′-didehydroribose; and        -   each R′ is independently hydroxyl or            where a is zero, one or two.

In the preferred ribopolynucleotides and 2′-deoxyribopolynucleotidesillustrated above, the nucleobases B are covalently attached to the C1′carbon of the sugar moiety as previously described.

“Polynucleotide Analog:” refers to a polynucleotide in which at leastone nucleoside monomer unit is a nucleoside analog and/or at least onephosphate ester internucleoside linkage is a phosphate ester analog, aspreviously defined. Also included within the definition ofpolynucleotide analogs are polynucleotides in which the phosphate esterand/or sugar phosphate ester internucleoside linkages are replaced withother types of linkages, such as N-(2-aminoethyl)-glycine amides andother amides (see, e.g., Nielsen et al., 1991, Science 254:1497-1500; WO92/20702; U.S. Pat. No. 5,719,262; U.S. Pat. No. 5,698,685) morpholinos(see U.S. Pat. No. 5,698,685; U.S. Pat. No. 5,378,841; U.S. Pat. No.5,185,144); carbamates (see Stirchak & Summerton, 1987, J. Org. Chem.52:4202); methylene(methylimino) (see Vasseur et al., 1992, J. Am. Chem.Soc. 114:4006); 3′-thioformacetals (see Jones et al., 1993, J. Org.Chem. 58:2983); sulfamates (see U.S. Pat. No. 5,470,967); and others(see, e.g., U.S. Pat. No. 5,817,781; Frier & Altman, 1997, Nucl. AcidsRes. 25:4429 and the references cited therein).

“Alkyl:” refers to a saturated or unsaturated, branched, straight-chainor cyclic monovalent hydrocarbon group derived by the removal of onehydrogen atom from a single carbon atom of a parent alkane, alkene oralkyne. Typical alkyl groups include, but are not limited to, methyl;ethyls such as ethanyl, ethenyl, ethynyl; propyls such as propan-1-yl,propan-2-yl, cyclopropan-1-yl, prop-1-en-1-yl, prop-1-en-2-yl,prop-2-en-1-yl, cycloprop-1-en-1-yl; cycloprop-2-en-1-yl,prop-1-yn-1-yl, prop-2-yn-1-yl, etc.; butyls such as butan-1-yl,butan-2-yl, 2-methyl-propan-1-yl, 2-methyl-propan-2-yl, cyclobutan-1-yl,but-1-en-1-yl, but-1-en-2-yl, 2-methyl-prop-1-en-1-yl, but-2-en-1-yl,but-2-en-2-yl, buta-1,3-dien-1-yl, buta-1,3-dien-2-yl,cyclobut-1-en-1-yl, cyclobut-1-en-3-yl, cyclobuta-1,3-dien-1-yl,but-1-yn-1-yl, but-1-yn-3-yl, but-3-yn-1-yl, etc.; and the like. Wherespecific levels of saturation are intended, the nomenclature “alkanyl,”“alkenyl” and/or “alkynyl” is used, as defined below. In preferredembodiments, the alkyl groups are (C₁-C₆) alkyl.

“Alkanyl:” refers to a saturated branched, straight-chain or cyclicalkyl group derived by the removal of one hydrogen atom from a singlecarbon atom of a parent alkane. Typical alkanyl groups include, but arenot limited to, methanyl; ethanyl; propanyls such as propan-1-yl,propan-2-yl (isopropyl), cyclopropan-1-yl, etc.; butyanyls such asbutan-1-yl, butan-2-yl (sec-butyl), 2-methyl-propan-1-yl (isobutyl),2-methyl-propan-2-yl (t-butyl), cyclobutan-1-yl, etc.; and the like. Inpreferred embodiments, the alkanyl groups are (C₁-C₆) alkanyl.

“Alkenyl:” refers to an unsaturated branched, straight-chain or cyclicalkyl group having at least one carbon-carbon double bond derived by theremoval of one hydrogen atom from a single carbon atom of a parentalkene. The group may be in either the cis or trans conformation aboutthe double bond(s). Typical alkenyl groups include, but are not limitedto, ethenyl; propenyls such as prop-1-en-1-yl, prop-1-en-2-yl,prop-2-en-1-yl, prop-2-en-2-yl, cycloprop-1-en-1-yl;cycloprop-2-en-1-yl; butenyls such as but-1-en-1-yl, but-1-en-2-yl,2-methyl-prop-1-en-1-yl, but-2-en-1-yl, but-2-en-1-yl, but-2-en-2-yl,buta-1,3-dien-1-yl, buta-1,3-dien-2-yl, cyclobut-1-en-1-yl,cyclobut-1-en-3-yl, cyclobuta-1,3-dien-1-yl, etc.; and the like. Inpreferred embodiments, the alkenyl group is (C₂-C₆) alkenyl.

“Alkynyl:” refers to an unsaturated branched, straight-chain or cyclicalkyl group having at least one carbon-carbon triple bond derived by theremoval of one hydrogen atom from a single carbon atom of a parentalkyne. Typical alkynyl groups include, but are not limited to, ethynyl;propynyls such as prop-1-yn-1-yl, prop-2-yn-1-yl, etc.; butynyls such asbut-1-yn-1-yl, but-1-yn-3-yl, but-3-yn-1-yl, etc.; and the like. Inpreferred embodiments, the alkynyl group is (C₂-C₆) alkynyl.

“Alkyldiyl:” refers to a saturated or unsaturated, branched,straight-chain or cyclic divalent hydrocarbon group derived by theremoval of one hydrogen atom from each of two different carbon atoms ofa parent alkane, alkene or alkyne, or by the removal of two hydrogenatoms from a single carbon atom of a parent alkane, alkene or alkyne.The two monovalent radical centers or each valency of the divalentradical center can form bonds with the same or different atoms. Typicalalkyldiyl groups include, but are not limited to methandiyl; ethyldiylssuch as ethan-1,1-diyl, ethan-1,2-diyl, ethen-1,1-diyl, ethen-1,2-diyl;propyldiyls such as propan-1,1-diyl, propan-1,2-diyl, propan-2,2-diyl,propan-1,3-diyl, cyclopropan-1,1-diyl, cyclopropan-1,2-diyl,prop-1-en-1,1-diyl, prop-1-en-1,2-diyl, prop-2-en-1,2-diyl,prop-1-en-1,3-diyl, cycloprop-1-en-1,2-diyl, cycloprop-2-en-1,2-diyl,cycloprop-2-en-1,1-diyl, prop-1-yn-1,3-diyl, etc.; butyldiyls such as,butan-1,1-diyl, butan-1,2-diyl, butan-1,3-diyl, butan-1,4-diyl,butan-2,2-diyl, 2-methyl-propan-1,1-diyl, 2-methyl-propan-1,2-diyl,cyclobutan-1,1-diyl; cyclobutan-1,2-diyl, cyclobutan-1,3-diyl,but-1-en-1,1-diyl, but-1-en-1,2-diyl, but-1-en-1,3-diyl,but-1-en-1,4-diyl, 2-methyl-prop-1-en-1,1-diyl,2-methanylidene-propan-1,1-diyl, buta-1,3-dien-1,1-diyl,buta-1,3-dien-1,2-diyl, buta-1,3-dien-1,3-diyl, buta-1,3-dien-1,4-diyl,cyclobut-1-en-1,2-diyl, cyclobut-1-en-1,3-diyl, cyclobut-2-en-1,2-diyl,cyclobuta-1,3-dien-1,2-diyl, cyclobuta-1,3-dien-1,3-diyl,but-1-yn-1,3-diyl, but-1-yn-1,4-diyl, buta-1,3-diyn-1,4-diyl, etc.; andthe like. Where specific levels of saturation are intended, thenomenclature alkanyldiyl, alkenyldiyl and/or alkynyldiyl is used. Inpreferred embodiments, the alkyldiyl group is (C₁-C₆) alkyldiyl. Alsopreferred are saturated acyclic alkanyldiyl groups in which the radicalcenters are at the terminal carbons, e.g., methandiyl (methano);ethan-1,2-diyl (ethano); propan-1,3-diyl (propano); butan-1,4-diyl(butano); and the like (also referred to as alkylenos, defined infra).

“Alkyleno:” refers to a straight-chain alkyldiyl group having twoterminal monovalent radical centers derived by the removal of onehydrogen atom from each of the two terminal carbon atoms ofstraight-chain parent alkane, alkene or alkyne. Typical alkyleno groupsinclude, but are not limited to, methano; ethylenos such as ethano,etheno, ethyno; propylenos such as propano, prop[1]eno, propa[1,2]dieno,prop[1]yno, etc.; butylenos such as butano, but[1]eno, but[2]eno,buta[1,3]dieno, but[1]yno, but[2]yno, but[1,3]diyno, etc.; and the like.Where specific levels of saturation are intended, the nomenclaturealkano, alkeno and/or alkyno is used. In preferred embodiments, thealkyleno group is (C₁-C₆) or (C₁-C₄) alkyleno. Also preferred arestraight-chain saturated alkano groups, e.g., methano, ethano, propano,butano, and the like.

“Heteroalkyl, Heteroalkanyl, Heteroalkenyl, Heteroalkanyl,Heteroalkyldiyl and Heteroalkyleno:” refer to alkyl, alkanyl, alkenyl,alkynyl, alkyldiyl and alkyleno groups, respectively, in which one ormore of the carbon atoms (and any associated hydrogen atoms) are eachindependently replaced with the same or different heteroatomic groups.Typical heteroatomic groups which can be included in these groupsinclude, but are not limited to, —O—, —S—, —O—O—, —S—S—, —O—S—, —NR′—,═N—N═, —N═N—, —N═N—NR′—, —PH—, —P(O)₂—, —O—P(O)₂—, —SH₂—, —S(O)₂—,—SnH₂— and the like, where each R′ is independently hydrogen, alkyl,alkanyl, alkenyl, alkynyl, aryl, arylaryl, arylalkyl, heteroaryl,heteroarylalkyl or heteroaryl-heteroaryl as defined herein.

“Acyclic Heteroatomic Bridge:” refers to a divalent bridge in which thebackbone atoms are exclusively heteroatoms. Typical acyclic heteroatomicbridges include, but are not limited to, any of the various heteroatomicgroups listed above, either alone or in combinations.

“Cyclic Heteroalkyl:” refers to a saturated or unsaturated cyclic alkylgroup in which one or more carbon atoms (and any associated hydrogenatoms) are independently replaced with the same or different heteroatom.Typical heteroatoms to replace the carbon atom(s) include, but are notlimited to, N, P, O, S, Si, etc. Where a specific level of saturation isintended, the nomenclature “cyclic heteroalkanyl” or “cyclicheteroalkenyl” is used. Typical cyclic heteroalkyl moieties include, butare not limited to, groups derived from epoxides, imidazolidine,morpholine, piperazine, piperidine, pyrazolidine, pyrrolidine,quinuclidine, and the like. In preferred embodiments, the cyclicheteroalkyl is a 3-6 membered cyclic heteroalkyl. Particularly preferredcyclic heteralkyls are morpholino, pyrrolidino, pipyridino,tetrahydrothiopheno, tetrahydrofuranyl and tetrahydropyranyl.

“Parent Aromatic Ring System:” refers to an unsaturated cyclic orpolycyclic ring system having a conjugated π electron system.Specifically included within the definition of “parent aromatic ringsystem” are fused ring systems in which one or more of the rings arearomatic and one or more of the rings are saturated or unsaturated, suchas, for example, indane, indene, phenalene, etc. Typical parent aromaticring systems include, but are not limited to, aceanthrylene,acenaphthylene, acephenanthrylene, anthracene, azulene, benzene,chrysene, coronene, fluoranthene, fluorene, hexacene, hexaphene,hexalene, αs-indacene, s-indacene, indane, indene, naphthalene,octacene, octaphene, octalene, ovalene, penta-2,4-diene, pentacene,pentalene, pentaphene, perylene, phenalene, phenanthrene, picene,pleiadene, pyrene, pyranthrene, rubicene, triphenylene, trinaphthalene,and the like

“Aryl:” refers to a monovalent aromatic hydrocarbon group derived by theremoval of one hydrogen atom from a single carbon atom of a parentaromatic ring system. Typical aryl groups include, but are not limitedto, groups derived from aceanthrylene, acenaphthylene,acephenanthrylene, anthracene, azulene, benzene, chrysene, coronene,fluoranthene, fluorene, hexacene, hexaphene, hexalene, as-indacene,s-indacene, indane, indene, naphthalene, octacene, octaphene, octalene,ovalene, penta-2,4-diene, pentacene, pentalene, pentaphene, perylene,phenalene, phenanthrene, picene, pleiadene, pyrene, pyranthrene,rubicene, triphenylene, trinaphthalene, and the like. In preferredembodiments, the aryl group is (C₅-C₁₄) aryl, with (C₅-C₁₀) being evenmore preferred. Particularly preferred aryls are cyclopentadienyl,phenyl and naphthyl.

“Aryldiyl:” refers to a divalent aromatic hydrocarbon group derived bythe removal of one hydrogen atom from each of two different carbon atomsof a parent aromatic ring system or by the removal of two hydrogen atomsfrom a single carbon atom of a parent aromatic ring system. The twomonovalent radical centers or each valency of the divalent center canform bonds with the same or different atom(s). Typical aryldiyl groupsinclude, but are not limited to, divalent groups derived fromaceanthrylene, acenaphthylene, acephenanthrylene, anthracene, azulene,benzene, chrysene, coronene, fluoranthene, fluorene, hexacene,hexaphene, hexalene, as-indacene, s-indacene, indane, indene,naphthalene, octacene, octaphene, octalene, ovalene, penta-2,4-diene,pentacene, pentalene, pentaphene, perylene, phenalene, phenanthrene,picene, pleiadene, pyrene, pyranthrene, rubicene, triphenylene,trinaphthalene, and the like. In preferred embodiments, the aryldiylgroup is (C₅-C₁₄) aryldiyl, with (C₅-C₁₀) being even more preferred. Themost preferred aryldiyl groups are divalent groups derived from benzeneand naphthalene, especially phena-1,4-diyl, naphtha-2,6-diyl andnaphtha-2,7-diyl.

“Aryleno:” refers to a divalent bridge group having two adjacentmonovalent radical centers derived by the removal of one hydrogen atomfrom each of two adjacent carbon atoms of a parent aromatic ring system.Attaching an aryleno bridge group, e.g. benzo, to a parent aromatic ringsystem, e.g. benzene, results in a fused aromatic ring system, e.g.naphthalene. The bridge is assumed to have the maximum number ofnon-cumulative double bonds consistent with its attachment to theresultant fused ring system. When an aryleno group is formed by takingtogether two adjacent substituents on a structure that includesalternative substituents, to avoid double-counting carbon atoms, thecarbon atoms of the aryleno bridge replace the bridging carbon atoms ofthe structure. As an example, consider the following structure:

-   -   wherein:        -   R¹, when taken alone is hydrogen, or when taken together            with R² is (C₅-C₁₄) aryleno; and        -   R², when taken alone is hydrogen, or when taken together            with R¹ is (C₅-C₁₄) aryleno.

When R¹ and R² are each hydrogen, the resultant compound is benzene.When R¹ taken together with R² is C₆ aryleno (benzo), the resultantcompound is naphthalene. When R¹ taken together with R² is C₁₀ aryleno(naphthaleno), the resultant compound is anthracene or phenanthrene.Typical aryleno groups include, but are not limited to, aceanthryleno,acenaphthyleno, acephenanthryleno, anthraceno, azuleno, benzeno (benzo),chryseno, coroneno, fluorantheno, fluoreno, hexaceno, hexapheno,hexaleno, αs-indaceno, s-indaceno, indeno, naphthaleno (naphtho),octaceno, octapheno, octaleno, ovaleno, penta-2,4-dieno, pentaceno,pentaleno, pentapheno, peryleno, phenaleno, phenanthreno, piceno,pleiadeno, pyreno, pyranthreno, rubiceno, triphenyleno, trinaphthaleno,and the like. Where a specific connectivity is intended, the involvedbridging carbon atoms (of the aryleno bridge) are denoted in brackets,e.g., [1,2]benzeno ([1,2]benzo), [1,2]naphthaleno, [2,3]naphthaleno,etc. Thus, in the above example, when R′ taken together with R² is[2,3]naphthaleno, the resultant compound is anthracene. When R′ takentogether with R² is [1,2]naphthaleno, the resultant compound isphenanthrene. In a preferred embodiment, the aryleno group is (C₅-C₁₄),with (C₅-C₁₀) being even more preferred.

“Arylaryl:” refers to a monovalent hydrocarbon group derived by theremoval of one hydrogen atom from a single carbon atom of a ring systemin which two or more identical or non-identical parent aromatic ringsystems are joined directly together by a single bond, where the numberof such direct ring junctions is one less than the number of parentaromatic ring systems involved. Typical arylaryl groups include, but arenot limited to, biphenyl, triphenyl, phenyl-naphthyl, binaphthyl,biphenyl-naphthyl, and the like. Where the number of carbon atoms in anarylaryl group are specified, the numbers refer to the carbon atomscomprising each parent aromatic ring. For example, (C₅-C₁₄) arylaryl isan arylaryl group in which each aromatic ring comprises from 5 to 14carbons, e.g., biphenyl, triphenyl, binaphthyl, phenylnaphthyl, etc.Preferably, each parent aromatic ring system of an arylaryl group isindependently a (C₅-C₁₄) aromatic, more preferably a (C₅-C₁₀) aromatic.Also preferred are arylaryl groups in which all of the parent aromaticring systems are identical, e.g., biphenyl, triphenyl, binaphthyl,trinaphthyl, etc.

“Biaryl:” refers to an arylaryl group having two identical parentaromatic systems joined directly together by a single bond. Typicalbiaryl groups include, but are not limited to, biphenyl, binaphthyl,bianthracyl, and the like. Preferably, the aromatic ring systems are(C₅-C₁₄) aromatic rings, more preferably (C₅-C₁₀) aromatic rings. Aparticularly preferred biaryl group is biphenyl.

“Arylalkyl:” refers to an acyclic alkyl group in which one of thehydrogen atoms bonded to a carbon atom, typically a terminal or sp³carbon atom, is replaced with an aryl group. Typical arylalkyl groupsinclude, but are not limited to, benzyl, 2-phenylethan-1-yl,2-phenylethen-1-yl, naphthylmethyl, 2-naphthylethan-1-yl,2-naphthylethen-1-yl, naphthobenzyl, 2-naphthophenylethan-1-yl and thelike. Where specific alkyl moieties are intended, the nomenclaturearylalkanyl, arylakenyl and/or arylalkynyl is used. In preferredembodiments, the arylalkyl group is (C₆-C₂₀) arylalkyl, e.g., thealkanyl, alkenyl or alkynyl moiety of the arylalkyl group is (C₁-C₆) andthe aryl moiety is (C₅-C₁₄). In particularly preferred embodiments thearylalkyl group is (C₆-C₁₃), e.g., the alkanyl, alkenyl or alkynylmoiety of the arylalkyl group is (C₁-C₃) and the aryl moiety is(C₅-C₁₀).

“Arylheteroalkyl:” refers to an acyclic heteroalkyl group in which oneof the hydrogen atoms bonded to a carbon or heteroatom, typically aterminal carbon or heteroatom, is replaced with an aryl group. Wherearylheteroalkyl moieties are having specified levels of saturationintended, the nomenclature aryl heteroalkanyl, aryl heteroalkenyl and/oraryl heteroalkynyl is used. In preferred embodiments, thearylheteroalkyl group is a 6-26 membered arylheteroalkyl, e.g., theheteroalkyl moiety is 1-6 membered and the aryl moiety is (C₅-C₂₀) aryl.In particularly preferred embodiments, the arylheteroalkyl group is 6-13membered, e.g., the heteroalkyl moiety is 1-3 membered and the arylmoiety is (C₅-C₁₀).

“Parent Heteroaromatic Ring System:” refers to a parent aromatic ringsystem in which one or more carbon atoms (and any associated hydrogenatoms) are each independently replaced with the same or differentheteroatom. Typical heteratoms to replace the carbon atoms include, butare not limited to, N, P, O, S, Si, etc. (Including and associatedhydrogen or other atoms). Specifically included within the definition of“parent heteroaromatic ring systems” are fused ring systems in which oneor more of the rings are aromatic and one or more of the rings aresaturated or unsaturated, such as, for example, arsindole, chromane,chromene, indole, indoline, xanthene, etc. Typical parent heteroaromaticring systems include, but are not limited to, arsindole, carbazole,β-carboline, chromane, chromene, cinnoline, furan, imidazole, indazole,indole, indoline, indolizine, isobenzofuran, isochromene, isoindole,isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine,oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline,phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole,pyridazine, pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline,quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole,thiophene, triazole, xanthene, and the like.

“Heteroaryl:” refers to a monovalent heteroaromatic group derived by theremoval of one hydrogen atom from a single atom of a parentheteroaromatic ring system. Typical heteroaryl groups include, but arenot limited to, groups derived from acridine, arsindole, carbazole,P-carboline, chromane, chromene, cinnoline, furan, imidazole, indazole,indole, indoline, indolizine, isobenzofuran, isochromene, isoindole,isoindoline, isoquinoline, isothiazole, isoxazole, naphthyridine,oxadiazole, oxazole, perimidine, phenanthridine, phenanthroline,phenazine, phthalazine, pteridine, purine, pyran, pyrazine, pyrazole,pyridazine, pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline,quinoline, quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole,thiophene, triazole, xanthene, and the like. In preferred embodiments,the heteroaryl group is a 5-14 membered heteroaryl, with 5-10 memberedheteroaryl being particularly preferred. The most preferred heteroarylgroups are those derived from thiophene, pyrrole, benzothiophene,benzofuran, indole, pyridine, quinoline, imidazole, oxazole andpyrazine.

“Heteroaryldiyl:” refers to a divalent heteroaromatic group derived bythe removal of one hydrogen atom from each of two different atoms of aparent heteroaromatic ring system or by the removal of two hydrogenatoms from a single atom of a parent heteroaromatic ring system. The twomonovalent radical centers or each valency of the single divalent centercan form bonds with the same or different atom(s). Typicalheteroaryldiyl groups include, but are not limited to, divalent groupsderived from acridine, arsindole, carbazole, β-carboline, chromane,chromene, cinnoline, furan, imidazole, indazole, indole, indoline,indolizine, isobenzofuran, isochromene, isoindole, isoindoline,isoquinoline, isothiazole, isoxazole, naphthyridine, oxadiazole,oxazole, perimidine, phenanthridine, phenanthroline, phenazine,phthalazine, pteridine, purine, pyran, pyrazine, pyrazole, pyridazine,pyridine, pyrimidine, pyrrole, pyrrolizine, quinazoline, quinoline,quinolizine, quinoxaline, tetrazole, thiadiazole, thiazole, thiophene,triazole, xanthene, and the like. In preferred embodiments, theheteroaryldiyl group is 5-14 membered heteroaryldiyl, with 5-10 memberedbeing particularly preferred. The most preferred heteroaryldiyl groupsare divalent groups derived from the preferred heteroaryls thiophene,pyrrole, benzothiophene, benzofuran, indole, pyridine, quinoline,imidazole, oxazole and pyrazine.

“Heteroaryleno:” refers to a divalent bridge group having two adjacentmonovalent radical centers derived by the removal of one hydrogen atomfrom each of two adjacent atoms of a parent heteroaromatic ring system.Attaching a heteroaryleno bridge group, e.g. pyridino, to a parentaromatic ring system, e.g. benzene, results in a fused heteroaromaticring system, e.g., quinoline. The bridge is assumed to have the maximumnumber of non-cumulative double bonds consistent with its attachment tothe resultant fused ring system. When a heteroaryleno substituent isformed by taking together two adjacent substituents on a structure thatincludes alternative substituents, to avoid double-counting ring atoms,the ring atoms of the heteroaryleno bridge replace the bridging ringatoms of the structure. As an example, consider the following structure:

-   -   wherein:        -   R¹, when taken alone is hydrogen, or when taken together            with R² is 5-14 membered heteroaryleno; and        -   R², when taken alone is hydrogen, or when taken together            with R′ is 5-14 membered heteroaryleno;

When R¹ and R² are each hydrogen, the resultant compound is benzene.When R¹ taken together with R² is a 6-membered heteroaryleno (e.g.,pyridino), the resultant compound is isoquinoline, quinoline orquinolizine. When R¹ taken together with R² is a 10-memberedheteroaryleno (e.g., isoquinoline), the resultant compound is, e.g.,acridine or phenanthridine. Typical heteroaryleno groups include, butare not limited to, acridino, carbazolo, β-carbolino, chromeno,cinnolino, furano, imidazolo, indazoleno, indoleno, indolizino,isobenzofurano, isochromeno, isoindoleno, isoquinolino, isothiazoleno,isoxazoleno, naphthyridino, oxadiazoleno, oxazoleno, perimidino,phenanthridino, phenanthrolino, phenazino, phthalazino, pteridino,purino, pyrano, pyrazino, pyrazoleno, pyridazino, pyridino, pyrimidino,pyrroleno, pyrrolizino, quinazolino, quinolino, quinolizino,quinoxalino, tetrazoleno, thiadiazoleno, thiazoleno, thiopheno,triazoleno, xantheno, and the like. Where a specific connectivity isintended, the involved bridging n atoms (of the heteroaryleno bridge)are denoted in brackets, e.g., [1,2]pyridino, [2,3]pyridino,[3,4]pyridino, etc. Thus, in the above example, when R¹ taken togetherwith R² is [1,2]pyridino, the resultant compound is quinolizine. When R¹taken together with R² is [2,3]pyridino, the resultant compound isquinoline. When R¹ taken together with R² is [3,4]pyridino, theresultant compound is isoquinoline. In preferred embodiments, theheteroaryleno group is 5-14 membered heteroaryleno, with 5-10 memberedbeing even more preferred. The most preferred heteroaryleno groups arethose derived from the preferred heteroaryls thiophene, pyrrole,benzothiophene, benzofuran, indole, pyridine, quinoline, imidazole,oxazole and pyrazine.

“Heteroaryl-Heteroaryl:” refers to a monovalent heteroaromatic groupderived by the removal of one hydrogen atom from a single atom of a ringsystem in which two or more identical or non-identical parentheteroaromatic ring systems are joined directly together by a singlebond, where the number of such direct ring junctions is one less thanthe number of parent heteroaromatic ring systems involved. Typicalheteroaryl-heteroaryl groups include, but are not limited to, bipyridyl,tripyridyl, pyridylpurinyl, bipurinyl, etc. Where the number of atomsare specified, the numbers refer to the number of atoms comprising eachparent heteroatomatic ring systems. For example, 5-14 memberedheteroaryl-heteroaryl is a heteroaryl-heteroaryl group in which eachparent heteroaromatic ring system comprises from 5 to 14 atoms, e.g.,bipyridyl, tripuridyl, etc. Preferably, each parent heteroaromatic ringsystem is independently a 5-14 membered heteroaromatic, more preferablya 5-10 membered heteroaromatic. Also preferred are heteroaryl-heteroarylgroups in which all of the parent heteroaromatic ring systems areidentical. The most preferred heteroaryl-heteroaryl groups are those inwhich each heteroaryl group is derived from the preferred heteroarylsthiophene, pyrrole, benzothiophene, benzofuran, indole, pyridine,quinoline, imidazole, oxazole and pyrazine.

“Biheteroaryl:” refers to a heteroaryl-heteroaryl group having twoidentical parent heteroaromatic ring systems joined directly together bya single bond. Typical biheteroaryl groups include, but are not limitedto, bipyridyl, bipurinyl, biquinolinyl, and the like. Preferably, theheteroaromatic ring systems are 5-14 membered heteroaromatic rings, morepreferably 5-10 membered heteroaromatic rings. The most preferredbiheteroaryl groups are those in which the heteroaryl groups are derivedfrom the preferred heteroaryls thiophene, pyrrole, benzothiophene,benzofuran, indole, pyridine, quinoline, imidazole, oxazole andpyrazine.

“Heteroarylalkyl:” refers to an acyclic alkyl group in which one of thehydrogen atoms bonded to a carbon atom, typically a terminal or sp³carbon atom, is replaced with a heteroaryl group. Where specific alkylmoieties are intended, the nomenclature heteroarylalkanyl,heteroarylakenyl and/or heterorylalkynyl is used. In preferredembodiments, the heteroarylalkyl group is a 6-20 memberedheteroarylalkyl, e.g., the alkanyl, alkenyl or alkynyl moiety of theheteroarylalkyl is 1-6 membered and the heteroaryl moiety is a5-14-membered heteroaryl. In particularly preferred embodiments, theheteroarylalkyl is a 6-13 membered heteroarylalkyl, e.g., the alkanyl,alkenyl or alkynyl moiety is 1-3 membered and the heteroaryl moiety is a5-10 membered heteroaryl.

“Substituted:” refers to a group in which one or more hydrogen atoms areeach independently replaced with the same or different substituent(s).Typical substituents include, but are not limited to, —X, —R, —O⁻, ═O,—OR, —SR, —S⁻, ═S, —NRR, ═NR, perhalo (C₁-C₆) alkyl, —CX₃, —CF₃, —CN,—OCN, —SCN, —NO, —NO₂, =N₂, —N₃, —S(O)₂O⁻, —S(O)₂OH, —S(O)₂R, —OS(O₂)O⁻,—OS(O)₂OH, —OS(O)₂R, —P(O)(O⁻)₂, —P(O)(OH)(O⁻), —OP(O)₂(O⁻), —C(O)R,—C(S)R, —C(O)OR, —C(O)O⁻, —C(S)OR, and —C(NR)NRR, where each X isindependently a halogen; each R is independently hydrogen, halogen,alkyl, alkanyl, alkenyl, alkynyl, aryl, arylalkyl, arylaryl,arylheteroalkyl, heteroaryl, heteroarylalkyl, heteroaryl-heteroaryl,—NR′R′, —C(O)R′ or —S(O)₂R′; and each R′ is independently hydrogen,alkyl, alkanyl, alkynyl, aryl, arylalkyl, arylheteralkyl, arylaryl,heteroaryl, heteroarylalkyl or heteroaryl-heteroaryl.

5.3 The Compounds

As discussed in the Background Section, the fluorescent dyes used tolabel polynucleotides in applications such as nucleic acid sequencingreactions frequently have a significant impact on their electrophoreticmobilities. These differences in electrophoretic mobilities areundesirable, as they can lead to significant ambiguities influorescence-based nucleic acid sequencing reactions, especially in4-color sequencing reactions where fragments terminated with differentterminating bases are separated in a single gel lane or capillary. Forexample, in 4-color Sanger-type nucleic acid sequencing methods, thebase sequence is determined by correlating a color with a terminationevent. The order of the colors directly yields the order of the basesequence in an electrophoresis experiment. A dye label can impose morethan a 10-12 base displacement in the electrophoretic mobility of alabeled fragment as compared with the corresponding unlabeled fragment.If all four labels impart the same mobility shift, then the correctorder of bands is obtained on the elcetrophoresis gel or trace. However,if one of the dye labels imparts a mobility shift that is different fromthat imparted by the other three, all fragments labeled with that dyewill be frame-shifted with respect to fragments labeled with the otherdyes. Since the fragments will electrophorese out of order, an incorrectsequence will be obtained.

As a consequence, efforts have been made to develop families of dyesthat induce minimal relative mobility shifts between labeledpolynucletide fragments (Ju et al., 1995, Proc. Natl. Acad. Sci. USA92:4347-4351; Ju et al., 1995, Anal. Biochem. 231:131-140; Ju et al.,1996, Nucl. Acids Res. 24:1144-1148; Metzker et al., 1996, Science271:1420-1422; Hung et al., 1996, Anal. Biochem. 243:15-27; Hung et al.,1997, Anal. Biochem. 252:78-88). In general, this has been accomplishedby adjusting the structure of the dye-DNA linker (Metzker et al., 1996,supra).

Recently, it has been discovered that such mobility shifts are much moreapparent with capillary array electrophoresis (CAE) than withtraditional slab gel electrophoresis (Marsh et al., 1997, J. CapillaryElectrophoresis 4:83-89). Thus, dyes exhibiting matched mobilities in aslab gel format may still display significant relative mobility shiftsin the more desirable, higher through-put CAE format (Tu et al., 1997,Nucl. Acids Res. 26:2797-2802). As a consequence of this observation,Bashkin and co-workers recently studied the electrophoretic mobilitiesof polynucleotides labeled with certain cyanine dyes (Tu et al., 1998,supra). Through these studies, it was found that several factors play arole in the observed electrophoretic mobilities of labeledpolynucleotides. Most notable are the net charge of the dye and theposition(s) of charged substituents on the dye. While certain trendswere noted, the authors simply catalogued observed electrophoreticmobilities. The authors did not study the effect of substitutions on thebiological activity of nucleotides labeled with the dyes.

The present invention provides a novel class of fluorescent cyanine dyecompounds that overcome this and other limitations in the art. Thecyanine dye compounds of the invention are substituted at one of theheteroaromatic ring nitrogen atoms with a pendant group carrying aplurality of charges (“mobility-modifying moiety”). By adjusting thenumber of charges carried by the pendant group, the electrophoreticmobilities of polynucleotides labeled with the mobility-modifyingcyanine dyes can be predictably adjusted or tuned to match theelectrophoretic mobilities of polynucleotides labeled with otherfluorescent dyes. Remarkably, the mobility-imparting characteristics ofa particular “parent” cyanine dye can be modified without significantlyaltering the spectral properties of the dye. Moreover,enzymatically-incorporable nucleotides and nucleotide analogs labeledwith the mobility-modifying dyes retain a high level of biologicalactivity as substrates for the polymerase enzymes commonly employed innucleic acid sequencing reactions, such as the thermostable polymeraseAMPLITAQ® DNA polymerase FS (PE Biosystems, Foster City, Calif.).Consequently, the mobility-modifying cyanine dyes of the inventionpermit sets of mobility-matched dyes and/or mobility-matched labelednucleosides/tides and analogs having specified spectral and/orbiological properties to be readily obtained.

The mobility-modifying cyanine dyes of the invention belong to thewell-recognized class of fluorescent molecules commonly known as cyaninedyes. Cyanine dyes generally comprise first and second parentnitrogen-containing heteroaromatic ring systems that are covalentlylinked together via a bridging moiety (see, e.g., U.S. Pat. No.5,569,587). The present invention concerns the class of cyanine dyes inwhich both parent heteroaromatic ring systems belong to the class ofrings generally referred to in the cyanine dye art asbenzazoles/benzazoliums.

Benzole/Benzazolium heteroaromatic ring systems have the followinggeneral structure:

-   -   wherein:        -   Z is selected from the group consisting of —S—, —O—, —Se—            and —CRR—, where each R, when taken alone, is independently            (C₁-C₆) alkyl, or when taken together with another R is            (C₄-C₅) alkyleno or (C₄-C₅) alkano. In the illustrated            structure, the dotted line indicates a bond which may be            either a single bond or a double bond. Since the            mobility-modifying dyes of the invention are substituted at            the ring nitrogen, whether the bond is a single bond or a            double bond will depend upon the nature of the C2            substituent. When the bond is a single bond, the ring system            is a benzazole. When the bond is a double bond, the ring            nitrogen is positively charged and the ring system is a            benzazolium. As will be described in more detail herein, the            various carbons at positions C4, C5, C6 and C7 may be            independently substituted with a variety of different            substituents.

In the above structure, when Z is S, the heteroaromatic ring system is asubstituted or unsubstituted benzothiazole/benzothiazolium; when Z is 0,the heteroaromatic ring system is a substituted or unsubstitutedbenzoxazole/benzoxazolium; when Z is Se, the heteroaromatic ring systemis a substituted or unsubstituted benzoselenazole/benzoselenazolium; andwhen Z is CRR, the heteroaromatic ring system is a substituted orunsubstituted indoline/indolinium.

While both rings belong to the same general class, they need not beidentical. Nor must they both be members of the same subclass. Forexample, one ring may be a substituted or unsubstitutedbenzoxazole/benzoxazolium and the other ring may be a substituted orunsubstituted indoline/indolinium. Mobility-modifying dyes of theinvention in which both rings are members of the same subclass arereferred to as “homodimers.” Those dyes in which each ring is a memberof a different subclass are referred to as “heterodimers.” Thesubstitution patterns of the rings of the homodimeric and/orheterodimeric dyes of the invention may be, but need not be, identical.

In the mobility-modifying cyanine dyes of the invention, theheteroaromatic ring nitrogen of one of the parent benzazole/benzazoliumring systems is substituted with a mobility-modifying moiety. Theheteroaromatic ring nitrogen of the other parent ring system issubstituted with a linking moiety for conjugating the mobility-modifyingcyanine dye to other molecules or substances. The nature of themobility-modifying and linking moieties are described in more detail,infra.

The heteroaromatic ring systems may be optionally substituted with oneor more of the same or different substituents, which can serve to alterthe spectral, chemical and/or physical properties of the dyes, as willbe described more fully below. The substitution patterns of each ringmay be, but need not be, identical. Thus, in one illustrative embodimentof the invention, the mobility-modifying cyanine dyes are compoundsaccording to structural formula (I):

-   -   wherein:        -   rings A and E are the same or different substituted or            unsubstituted benzazole/benzazolium heteroaromatic ring            systems;        -   “L-LG” represents a linking moiety for conjugating the            mobility-modifying cyanine dye to another molecule or            substance, where L is a linker and LG is a linking group;        -   “bridge” is a bridging moiety linking the            benzazole/benzazolium heteroaromatic ring systems A and E to            one another at their respective C-2 carbon atoms; and        -   “MM” is a mobility-modifying moiety.

As will be discussed in more detail below, in structural formula (I),both the “L” and “MM” substituents comprise a terminal alkyldiyl groupthat is bonded to the heteroaromatic ring nitrogen such that the bondlinking these substituents to their respective nitrogens of rings A andE is a N—CRR bond, where each R is independently hydrogen or (C₁-C₆)alkyl.

The attachment of the mobility-modifying moiety and linking moiety todifferent heteroaromatic ring nitrogens constitutes an important featureof the mobility-modifying dyes of the invention that has severalimportant consequences. It is well-known that substituting the aromaticrings of chromophores and fluorophores such as cyanine dyes frequentlyalters their spectral properties in an unpredictable fashion. While notcompletely understood, it is believed that such spectral changes are duein part to perturbations of the electronic delocalization of thechromophore or fluorophore. Attaching the mobility-modifying and linkingmoieties to heteroaromatic ring nitrogens minimizes these spectralchanges, resulting in mobility-modifying cyanine dyes having spectralproperties that are substantially similar to those of the respectiveunmodified dyes. As a consequence, once a dye having desirable spectralproperties is identified, it can be simply modified according to theprinciples described herein to predictably alter its influence on theelectrophoretic mobilities of polynucleotides labeled with the resultantmobility-modifying dye without altering its spectral properties.Moreover, placing the mobility-modifying and linking moieties ondifferent heteroaromatic ring systems permits the dyes to be conjugatedto nucleotides and nucleotide analogs without affecting the ability ofthe resultant labeled nucleotides and nucleotide analogs to act assubstrates for polymerizing enzymes.

Based on the above, those of skill in the art will appreciate thatvirtually any benzazole/benzazolium cyanine dye that is now known in theart or that is later developed can be advantageously mobility-modifiedaccording to the principles described herein. Thus, heteroaromatic ringsA and E can each be independently selected from amongst the plethora ofbenzazole/benzazolium ring systems commonly used in cyanine dyes. Suchring systems include, for example, the substituted and unsubstitutedbenzazole/benzazolium ring systems comprising the cyanine, merocyanineand styryl dyes described in U.S. Pat. Nos. 5,486,616, 5,569,587,5,569,766, 5,627,027; the substituted and unsubstitutedbenzazole/benzazolium ring systems comprising the asymmetric cyaninedyes described in U.S. Pat. Nos. 5,321,130, 5,410,030, 5,436,134,5,534,416, 5,582,977, 5,658,751, 5,656,449 and 5,863,753; thesubstituted and unsubstituted benzazole/benzazolium ring systemscomprising the sulfonated cyanine dyes described in Tu et al., 1998,Nucl. Acids Res. 26(11):2797-2802; and the various substituted andunsubstituted benzazole/benzazolium ring systems described in Brooker etal., 1945, “Absorption Spectra of Dyes with Heteroaromatic Nuclei—Colorand Constitution. Part VII. Interpretation of Absorptions of DyesContaining Heterocyclic Nuclei of Different Basicities,” J. Am. Chem.Soc. 67:1875-1889 (particularly at page 1878), the disclosures of whichare incorporated herein by reference. In order to obtainmobility-modifying cyanine dyes according to the invention from thesevarious rings, the substituent at one of the heteroaromatic ringnitrogens is replaced with a mobility-modifying moiety and thesubstituent at the other heteroaromatic ring nitrogen is replaced with alinking moiety as described herein.

In a preferred embodiment of the invention, the mobility-modifying dyesof the invention are homodimers, i.e., benzazole/benzazolium rings A andE are members of the same subclass, although they may have differentpatterns of substitution. More preferably, benzazole/benzazolium rings Aand E are the same or different substituted or unsubstitutedindoline/indolinium ring systems. Various mobility-modifying dyescomprised of a variety of different benzazole/benzazolium rings aredescribed in more detail, infra.

Benzazole/benzazolium rings A and E are covalently attached to oneanother via their C2 carbons by a bridging moiety designated “bridge” instructural formula (I). Those of skill in the art will appreciate thatvirtually any bridging moiety employed in the art to covalently attachthe parent rings of cyanine dyes to one another can be used to attachrings A and E to one another. Suitable bridging moieties are described,for example, in Polymethine Dyes Structure and Propterties, NikolaiTyutyukov et al., St. Kliment Ohridski University Press, 1991, thedisclosure of which is incorporated herein by reference.

Preferably, rings A and E are attached to one another with bridges thatpermit extensive electronic delocalization. Bridges permitting extensiveelectron delocalization include, but are not limited to, methine,polymethine, squarine and cyclic alkylene bridges. The various carbonatoms of the bridges may be optionally substituted with one or more ofthe same or different substitutents, which are typically selected fromthe group consisting of (C₁-C₆) alkyl, halogen, fluorine, chlorine, CN,CF₃, (C₅-C₁₄) aryl and 5-14 membered heteroaryl. In one embodiment, thebridge is a methine or polymethine bridge according to structuralformula (B.1):—(CR¹═CR²)_(k)—(CR³═CR⁴)_(f)—(CR⁵═CR⁶)_(m)—CR⁷═  (B. 1)

-   -   where:        -   k, l and m are each independently integers from 0 to 1; and        -   R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are each independently            selected from the group consisting of hydrogen, halogen, —F,            —Cl, —CN, —CF₃, (C₁-C₆) alkyl, (C₅-C₁₄) aryl or 5-14            membered heteroaryl.

For the polymethine bridges of structural formula (B. 1), the number ofmethine groups (—CH═) between the heteroaromatic ring systems influencesthe spectral properties of the dye (see, e.g., Brooker et al., supra).Generally, the greater the number of methine groups, the longer thewavelengths of the absorption and emission sprectra. Thus, the lengthand composition of the bridge can be adjusted to tune the spectralproperties of the dye as desired. For dyes designed to fluoresce whenexcited using a red (630-650 nm) excitation source, preferredpolymethine bridges are those in which the sum of k, l and m is 2.Particularly preferred methine and polymethine bridges are those inwhich R¹, R², R³, R⁴, R⁵, R⁶ and R⁷, if present, are each hydrogen. Aparticularly preferred polymethine bridge is —CH═CH—CH═CH—CH═.

In another embodiment, the bridge comprises a 4-6 membered cyclicalkylene or cyclic heteroalkylene, which may be optionally substitutedor unsubstituted, and which may also include optional flanking methineor polymethine units. The optional flanking methine or polymethine unitsmay be substituted or unsubstituted, as previously described for thepolymethine bridges of formula (B.1). The cyclic alkylene orheteroalkylene, and any optional flanking methine or polymethine units,forms an allylic system which permits extensive electron delocalization.In a preferred embodiment, the cyclic alkylene bridge is a compoundaccording to structural formula (B.2):

-   -   wherein:        -   p is an integer from 0 to 2;        -   R¹ and R⁷ are as previously defined for structural formula            (B.1); and        -   R¹⁰ and R^(10′) are each independently selected from the            group consisting of hydrogen, oxygen, halogen, —F, —Cl, —CN,            —CF₃, —OR, —SR, —NRR, (C₁-C₆) alkyl, (C₁-C₁₄) aryl or 5-14            membered heteroaryl, where each R is independently hydrogen            or (C₁-C₆) alkyl.

In structural formula (B.2), the dotted lines at substituents R¹⁰represent bonds that may be either single bonds or double bonds,depending upon the substituent. For example, when R^(10′) is oxygen, itmay be double-bonded to the carbon, forming a carbonyl substituent.

In a preferred embodiment, bridges according to structural formula (B.2)include those compounds in which p is 2 or 3 and/or R¹, R⁷, R¹⁰ andR^(10′) are each hydrogen.

In another preferred embodiment, bridges according to structural formula(B.2) include those compounds in which p is 0; R¹ and R⁷ are eachhydrogen; R¹⁰ and R^(10′) are each oxygen and the bond connectingsubstituent R^(10′) is a double bond.

Mobility-modifying moiety MM constitutes the key feature of themobility-modifying cyanine dyes of the invention. By manipulating MM,cyanine dyes having the desired electrophoretic mobility properties canbe readily obtained. The mobility-modifying moiety generally comprises apendant group bearing one or more charges through substitution with oneor more of the same or different anionic or cationic substituents. Thependant group can be any moiety capable of being substituted with thedesired number of charged substituents, but is typically a group havingthe structure -D-D′, where D is a bond, (C₁-C₆) alkyldiyl, 2-6 memberedheteroalkyldiyl or 1-6 membered acyclic heteroatomic bridge; and D is(C₁-C₆) alkyl, 2-6 membered heteroalkyl, (C₅-C₁₄) aryl, (C₅-C₁₄)arylaryl, 5-14 membered heteroaryl or 5-14 memberedheteroaryl-heteroaryl. Preferably, D is a bond when D′ is (C₁-C₆) alkylor 2-6 membered heteroalkyl; or D is (C₁-C₆) alkyleno when D′ is(C₅-C₁₄) aryl, (C₅-C₁₄) arylaryl, 5-14 membered heteroaryl or 5-14membered heteroaryl-heteroaryl. Preferred amongst the various D′ groupsare linear and branched (C₃-C₆) alkyls (especially alkanyls), linear andbranched 3-6 membered heteroalkyls (especially heteroalkanyls), (C₄-C₈)cycloalkyls (especially cycloalkanyls and cyclohexanyl), 4-8-memberedheterocycloalkyls (especially heterocycloalkanyls and piperidyl),(C₅-C₁₀) aryls (especially phenyl and naphthyl), (C₅-C₁₀) arylaryls(especially biaryls and biphenyl), 5-10 membered heteroaryls (especiallypyridyl, pyrrolyl, indolyl, quinolinyl, thiophenyl, and benzothiophenyl)and 5-10 membered heteroaryl-heteroaryls (especially biheteroarylscomposed of the above preferred heteroaryls).

Attaching aromatic rings such as aryl, arylaryl, heteroaryl andheteroaryl-heteroaryl groups directly to the heteroaromatic ringnitrogen of benzazole/benzazolium cyanine dyes has an unpredictablylarge effect on the absorbance and emission spectral properties of thecyanine dye. To avoid imposing these unpredictable spectral shifts,substituent D should be selected such that substituent D′ is attached tothe heteroaromatic ring nitrogen via an alkyldiyl group. When D′ is(C₅-C₁₄) aryl, (C₅-C₁₄) arylaryl, 5-14 membered heteroaryl or 5-14membered heteroaryl-heteroaryl, substituent D is typically a (C₁-C₆)alkyldiyl, preferably a (C₁-C₆) alkyleno and more preferably a (C₁-C₆)alkano such as methano (—CH₂—), ethano (—CH₂CH₂—), propano(—CH₂CH₂CH₂—), etc. These D groups separate the mobility-modifyingmoiety from the heteroaromatic ring nitrogen so as not to adverselyaffect the spectral characteristics of the resultant dye. The aromaticrings may be attached directly to the benzazole/benzazolium ringnitrogen when spectral shifts are desired. The most preferred pendantgroups according to structure -D-D′ are those in which D is (C₁-C₆)alkyleno or (C₁-C₆) alkano and D′ is phenyl, pyridyl, pyrrolyl, indolyl,quinolinyl, thiophenyl or benzothiophenyl; and those in which D is abond and D′ is (C₃-C₆) alkyl, especially (C₃-C₆) alkanyl.

Whether anionic or cationic charged substituents are used to substitutethe pendant group will depend upon the direction of the desired mobilityshift. When an increase in relative electrophoretic mobility is desired,the pendant group is substituted with anionic substitutents. When adecrease in relative electrophoretic mobility is desired, the pendantgroup is substituted with cationic substituents. These substituents aredescribed in more detail below.

The magnitude of the electrophoretic mobility shifts imparted by themobility-modifying dyes of the invention relative to polynucleotideslabeled with the corresponding unmodified dye (or another dye ofinterest) is related to the net charge of mobility-modifying moiety MM.The net charge of MM is in turn dependent upon the number and identitiesof charged substituents comprising the pendant group. For chargedsubstituents that are completely ionized at approximately neutral pH(i.e., a pH in the range of 6 to 8), it has been discovered that theelectrophoretic mobility increases linearly with net charge, i.e., eachunit increase or decrease that the mobility-modifying moiety MMcontributes to the net charge of the dye alters the electrophoreticmobility of polynucleotides labeled with the mobility-modifying dye byone nucleotide relative to polynucleotides labeled with thecorresponding unmodified dye. Thus, approximately one net charge shouldbe added to the mobility-modifying moiety for each nucleotide change inrelative electrophoretic mobility desired.

In order to add charges in a predictable manner, substituents havingpermanent charges or that are completely ionized at the pHs commonlyemployed in nucleic acid electrophoresis applications (typically in therange of pH 6 to pH 10) are preferred. Suitable cationic substituentsinclude, by way of example and not limitation, quarternary ammoniumgroups and groups having a pK_(a) of 8 or greater, including for example—NRR, —NRRR⁺, morpholino and piperidino, where each R is independentlyhydrogen or (C₁-C₆) alkyl (and any associated counterions). Preferredcationic substituents are quaternary ammoniums of the formula —N⁺RRR,where each R is independently (C₁-C₆) alkyl. When multiple cationicsubstituents are used, each substituent may be the same or different.Suitable anionic substituents are groups having a pK_(a) of about 6 orless, preferably 3 or less, and include by way of example and notlimitation, —C(O)O⁻, —P(O)(O⁻)₂, —P(O)(OH)(O⁻), —O—P(O)₂(O⁻), —S(O)₂O⁻and —O—S(O)₂O⁻ (including any associated counterions).

The charged substituents can be attached directly to the pendant group,or may be spaced away form the pendant group through one or moreintervening atoms, such as through a (C₁-C₆) alkyldiyl, a (C₁-C₆)alkyleno, a 1-6 membered heteroalkyldiyl or a 2-6 memberedheteroalkyleno group or, alternatively through a 2-6 membered acyclicbridge. Selecting the appropriate number(s) and identity(ies) of chargedsubstituents to achieve a desired change in electrophoretic mobilitybased upon the pK_(a) of the desired charged substituent, pH of theassay and net charge of the dye to be mobility-modified is within thecapabilities of those having skill in the art.

In embodiments where the mobility-modifying cyanine dye includes alinking moiety comprising a linking group capable of covalentlyconjugating the dye to another molecule (discussed infra), theselectivity of the conjugation reaction can be conveniently controlledby selecting charged substituents that do not react or become activatedunder the conjugation conditions. Due to their non-reactive nature inthe presence of a variety of conjugating reagents and conditions andtheir low pK_(a), —S(O)₂O⁻ and —O—S(O)₂O⁻ are preferred anionicsubstituents, especially in instances where a carboxyl or carboxylategroup is used to covalently conjugate the modified dye to the othermolecules or substances.

In addition to the charged substituents, the pendant group may befurther substituted with one or more additional substituents withoutadversely affecting the spectral properties or relative electrophoreticmobility change achieved. Such substituents can serve a variety ofpurposes. For example, polar substituents can increase the watersolubility of the mobility-modifying dye and sterically bulkysubstituents can decrease non-specific binding of the mobility-modifyingdye, as well as decrease the interactions between dyes in moleculeslabeled with multiple dyes, thereby decreasing fluorescence quenching.Substituents capable of imparting these and other desirable propertieswill be apparent to those having skill in the art.

Virtually any substituent that does not adversely affect the impartedmobility shift and/or other desirable properties of themobility-modifying dyes can be used. Typically, such additionalsubstituents are uncharged at the desired pH of use. Thus, additionaluncharged substituents that can be used to substitute the pendant groupinclude, but are not limited to, (C₁-C₆) alkyl, (C₁-C₆) alkylindependently substituted with one or more W, 2-6 membered heteroalkyl,2-6 membered heteroalkyl independently substituted with one or more W,(C₅-C₁₀) aryl, (C₅-C₁₀) aryl independently substituted with one or moreW, (C₅-C₆) arylaryl, (C₅-C₆) arylaryl independently substituted with oneor more W, (C₆-C₁₆) arylalkyl, (C₆-C₁₆) independently substituted withone or more W, 6-16 membered arylheteroalkyl, 6-16 memberedarylheteroalkyl independently substituted with one or more W, 5-10membered heteroaryl, 5-10 membered heteroaryl independently substitutedwith one or more W, 5-6 membered heteroaryl-heteroaryl, 5-6 memberedheteroaryl independently substituted with one or more W, 6-16 memberedheteroarylalkyl, 6-16 membered heteroarylalkyl independently substitutedwith one or more W, 6-16 membered heteroaryl-heteroalkyl and 6-16membered heteroaryl-heteroalkyl independently substituted with one ormore W, wherein:

-   -   each W is independently —R, —X, ═O, —OR, ═S, —SR, —NRR, ═NR,        (C₁-C₆) perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO, —NO₂, =N₂,        —N₃, —NHOH, —S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′,        —C(O)SR′, —C(S)SR′, and —C(NR)NRR;    -   each X is independently a halogen (preferably —F, —Cl or —Br);    -   each R is independently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆)        alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl,        (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl, 5-10 membered heteroaryl or        6-16 membered heteroarylalkyl; and    -   each R′ is independently (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)        alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl,        5-10 membered heteroaryl or 6-16 membered heteroarylalkyl; and        each R″ is independently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl,        (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10        membered heroaryl or 6-16 membered heteroarylalkyl. The various        R, R′ and R″ groups can be further substituted with one or more        of the same or different W groups, as defined above.

Such additional substituents are preferably groups that do not react orbecome activated under the conditions used to conjugate the dyes toother molecules or substances.

In a preferred embodiment, if present, any additional substituents areeach independently selected from the group consisting of (C₁-C₆) alkyl,(C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, —X, —OR, —NRR, —CF₃,—CN, —NO₂, and —C(O)R, where each R is independently hydrogen, —NR′R′,—C(O)R′, —S(O)₂R′, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl or(C₂-C₆) alkynyl; each R′ is independently hydrogen, (C₁-C₆) alkyl,(C₁-C₆) alkanyl, (C₂-C₆) alkenyl or (C₂-C₆) alkynyl; and X is —F, —Cl or—Br. Most preferably, the mobility-modifying moiety does not include anyadditional substituents.

As will be recognized by those having skill in the art, thehydrophobicity of the pendant group and the net charge of mobilitymodifying moiety MM can affect the water-solubility of the resultantmobility-modifying cyanine dye. As mobility-modifying dyes that aresoluble in the aqueous buffers and solutions commonly employed innucleic acid sequencing reactions and/or hybridization assays aredesired, the hydrophobicity of the pendant group and net negative chargeof mobility-modifying moiety MM should be adjusted so that the resultantdye is soluble in these buffers and solutions. Generally, thehydrophobicity of the pendant group can increase with increasing netcharge of MM. Skilled artisans can readily select an appropriatecombination of pendant group hydrophobicity and net charge of MM so asto retain the desired degree of solubility for particular applications.

It has been discovered that polynucleotides labeled with conventionalcyanine dyes, such as the mono-sulfonated benzo cyanine dye BenzoCy5,illustrated below:

have electrophoretic mobilities that are up to four bases slower thanpolynucleotides labeled with dibenzorhodamine dyes (see, e.g, U.S. Pat.No. 5,936,087) or extended rhodamine dyes (see, e.g., U.S. applicationSer. No. 09/325,243; attorney docket no. 4446). Replacing themono-sulfonated alkyl group on the BenzoCy5 dye with the mobilitymodifier 2,4-bis-sulfonatophenylmethan-1-yl to yield theMobility-Modifying BenzoCy5 dye illustrated below increased the relativeelectrophoretic mobilities of labeled polynucleotides by one base:

As red-emitting dyes such as dibenzo- and extended rhodamines possessdesirable characteristics for nucleic acid sequencing applications,preferred mobility-modifying dyes of the invention are those that haveelectrophoretic mobilities that are matched to these rhodamine dyes.Such mobility-modifying dyes will typically have mobility-modifyingmoieties that bear from 2 to 7 anionic substituents, more typically from2 to 5 anionic substituents, depending upon the identity of therhodamine dye being mobility-matched and the overall net charge of thesubstituent substituting the benzazole/benzazolium heteroaromatic rings.

Thus, in a preferred embodiment of the invention, mobility-modifyingmoiety MM is a substituted arylalkanyl according to structural formula(MM.1):

-   -   wherein:        -   n is an integer from 1 to 6 (preferably 1 to 3);        -   R²⁴, when taken alone, is hydrogen, a strong anionic            substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together            with R²⁵ is a benzo group or a benzo group independently            substituted with one or more strong anionic substituents,            —S(O)₂O⁻, or —O—S(O)₂O⁻ groups;        -   R²⁵, when taken alone, is hydrogen, a strong anionic            substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together            with R²⁴ or R²⁶ is a benzo group or a benzo group            independently substituted with one or more strong anionic            substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups;        -   R²⁶, when taken alone, is hydrogen, a strong anionic            substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together            with R²⁵ or R²⁷ is a benzo group or a benzo group            independently substituted with one or more strong anionic            substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups; and        -   R²⁷, when taken alone, is hydrogen, a strong anionic            substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together            with R²⁶ or R²⁸ is a benzo group or a benzo group            independently substituted with one or more strong anionic            substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups;        -   R²⁸, when taken alone, is hydrogen, a strong anionic            substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together            with R²⁷ is a benzo group or a benzo group independently            substituted with one or more strong anionic substituents,            —S(O)₂O⁻, or —O—S(O)₂O⁻ groups,        -   with the proviso that MM has a net charge of at least about            −1 at a pH in the range of about pH 6 to pH 10.

In a particularly preferred embodiment according to structural formula(MM.1), at least two of R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ are other thanhydrogen and n is 1.

In another particularly preferred embodiment according to structuralformula (MM.1), n is 1; R²⁴ and R²⁶ are each independently —S(O)₂O⁻ or—O—S(O)₂O⁻, preferably —S(O)₂O⁻; and R²⁵, R²⁷ and R²⁸ are each hydrogen.

In another particularly preferred embodiment according to structuralformula (MM.1), at least three of R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ are otherthan hydrogen and n is 1.

In still another particularly preferred embodiment according tostructural formula (MM.1), at least four of R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸are other than hydrogen and n is 1.

In another particularly preferred embodiment according to structuralformula (MM.1), at least five of R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ are otherthan hydrogen and n is 1.

In another preferred embodiment of the invention, mobility-modifyingmoiety MM is a substituted alkanyl according to structural formula(MM.2):

-   -   wherein:        -   o is an integer from 1 to 3;        -   q is an integer from 1 to 3;        -   R²⁹ is a strong anionic substituent, —S(O)₂O⁻ or —O—S(O)₂O⁻,        -   each R³⁰ is independently selected from the group consisting            of hydrogen a strong anionic substituent, —S(O)₂O⁻ and            —O—S(O)₂O⁻; and        -   R³¹ is selected from the group consisting of hydrogen, a            strong anionic substitutent, —S(O)₂O⁻, —O—S(O)₂O⁻ and —CH₃,        -   with the proviso that MM has a net charge of at least −2 at            a pH in the range of about pH 6 to pH 10.

In a particularly preferred embodiment of mobility-modifying moietiesaccording to structural formula (MM.2), at least one of R³⁰ is a stronganionic substituent, —S(O)₂O⁻ or —O—S(O)₂O⁻, preferably —S(O)₂O⁻ or—O—S(O)₂O⁻.

In another particularly preferred embodiment according to structuralformula (MM.2), o is 1; q is 1; R³⁰ is —S(O)₂O⁻ or —O—S(O)₂O⁻; and R³¹is —CH₃.

The mobility-modifying cyanine dyes of the invention include a linkingmoiety of the formula -L-LG, where L is a linker and LG is a linkinggroup, for conjugating the dyes to other molecules or substances. Thenature of linker L and linking group LG will depend upon the particularapplication and the type of conjugation desired. The linker can behydrophilic or hydrophobic, long or short, rigid, semirigid or flexible,depending upon the particular application. The linker can be optionallysubstituted with one or more substituents or one or more additionallinking groups, which may be the same or different than linking groupLG, thereby providing a “polyvalent” linking moiety capable ofconjugating with multiple molecules or substances. Preferably, however,linker L does not include such additional substituents or linkinggroups.

A wide variety of linkers L comprised of stable bonds suitable forspacing linking groups such as LG from molecules are known in the art,and include by way of example and not limitation, alkyldiyls,substituted alkyldiyls, alkylenos, substituted alkylenos,heteroalkyldiyls, substituted heteroalkyldiyls, heteroalkylenos,substituted heteroalkylenos, acyclic heteroatomic bridges, aryldiyls,substituted aryldiyls, arylaryldiyls, substituted arylaryldiyls,arylalkyldiyls, substituted arylalkyldiyls, heteroaryldiyls, substitutedheteroaryldiyls, heteroaryl-heteroaryldiyls, substitutedheteroaryl-heteroaryldiyls, heteroarylalkyldiyls, substitutedheteroarylalkyldiyls, heteroaryl-heteroalkyldiyls, substitutedheteroaryl-heteroalkyldiyls, and the like. Thus, linker L may includesingle, double, triple or aromatic carbon-carbon bonds,nitrogen-nitrogen bonds, carbon-nitrogen, carbon-oxygen bonds and/orcarbon-sulfur bonds, and may therefor include functionalities such ascarbonyls, ethers, thioethers, carboxamides, sulfonamides, ureas,urethanes, hydrazines, etc. In one embodiment, linker L has from 1-20non-hydrogen atoms selected from the group consisting of C, N, O, and Sand is composed of any combination of ether, thioether, amine, ester,carboxamide, sulfonmide, hydrazide, aromatic and heteroaromatic bonds.

Choosing a linker having properties suitable for a particularapplication is within the capabilities of those having skill in the art.For example, where a rigid linker is desired, L may be a rigidpolypeptide such as polyproline, a rigid polyunsaturated alkyldiyl or anaryldiyl, biaryldiyl, arylarydiyl, heteroaryldiyl, biheteroaryldiyl,heteroaryl-heteroaryldiyl, etc. Where a flexible linker is desired, Lmay be a flexible polypeptide such as polyglycine or a flexiblesaturated alkanyldiyl or heteroalkanyldiyl. Hydrophilic linkers may be,for example, polyalcohols or polyethers such as polyalkyleneglycols.Hydrophobic linkers may be, for example, alkyldiyls or aryldiyls.Linkers suitable for use in most biological applications include(C₁-C₁₂) alkyldiyls, particularly alkanylenos such as methano (—CH₂—),ethano (—CH₂—CH₂—), propano (—CH₂—CH₂—CH₂—), butano (—CH₂—CH₂—CH₂—CH₂—),pentano (—CH₂—CH₂—CH₂—CH₂—CH₂—) and hexano (—CH₂—CH₂—CH₂CH₂—CH₂—CH₂—);and (C₆-C₂₆) arylalkyldiyls, particularly those having the structuralformula —(CH₂)_(i)-φ- or —(CH₂)_(i)-φ-, where each i is independently aninteger from 1 to 6, φ is phenyldiyl (especially phena-1,3-diyl orphena-1,4-diyl) and Ψ is naphthyldiyl (especially naphtha-2,6-diyl ornaphtha-2,7-diyl). Analogs of these linkers L containing one or moreheteroatoms, particularly heteroartoms selected from the groupconsisting of O, S, N and NR″, where R″ is hydrogen or (C₁-C₆) alkyl,can also be conveniently used to space linking group LG from the dyes ofthe invention. Linkers L tailored to specific applications are discussedin more detail, infra.

The dyes can be conjugated to a variety of different molecules andsubstances using a plethora of different conjugation means. For example,the conjugation can be mediated via hydrophobic interactions, ionicattraction, through the use of pairs of specific binding molecules suchas biotin and avidin/streptavidin or through covalent attachment. Whenconjugation via hydrophobic interactions is desired, linking group LG isa hydrophobic moiety that is capable of forming hydrophobic interactionswith a hydrophobic moiety on the molecule or substance to be conjugated.Typical hydrophobic moieties include, but are not limited to,unsubstituted and substituted aryl, arylalkyl, arylaryl, heteroaryl,heteroarylaklyl and heteroaryl-heteroaryl groups. When the hydrophobicmoiety is substituted, the substituents are preferably nonpolar, morepreferably hydrophobic. Suitable hydrophobic moieties for formingnon-covalent conjugates will be apparent to those of skill in the art.

When conjugation via ionic attraction is desired, linking group LG is acharged moiety having a net charge of a polarity opposite to a netcharge on the molecule or substance to be conjugated. Typical chargedmoieties include, by way of example and not limitation, quaternaryammoniums, carboxylates and sulfonates, including salts thereof. Avariety of cyclic quaternary ammoniums that are suitable for use as LGare described in U.S. Pat. No. 5,863,753 (see, e.g., Cols. 8-9), thedisclosure of which is incorporated herein by reference.

When conjugation via pairs of specific binding molecules such as biotinand avidin/streptavidin is desired, LG will constitute one member of thebinding pair. The molecule or substance to be conjugated will bear theother member of the binding pair. Where one of the members of thespecific binding pair is a small molecule, such as biotin or a hormone,that member preferably comprises LG. A variety of biotins capable ofbeing covalently linked to reactive functional groups such as amines arecommercially available (e.g., Molecular Probes, Eugene, Oreg.). Thesebiotins can be incorporated into the dyes of the invention to yieldbiotin-labeled dyes suitable for non-covalent conjugation to a varietyof avidin/streptavidin-labeled molecules or substances.

Other representative specific binding pairs that can comprise linkinggroup LG are provided in TABLE 1, infra. TABLE 1 Representative SpecificBinding Pairs biotin avidin (or streptavidin or anti-biotin) IgG proteinA or protein G drug drug receptor toxin toxin receptor carbohydratelectin or carbohydrate receptor peptide peptide receptor protein proteinreceptor enzyme inhibitor enzyme DNA (RNA) complementary DNA (RNA)hormone hormone receptor

Preferably, linking group LG is capable of mediating conjugation viacovalent attachment. In this preferred embodiment, linking group LG istypically a reactive functional group (R_(x)). Covalent conjugates areobtained by reacting a dye of the invention including a reactive groupR_(x) with a molecule or substance that contains, or is modified tocontain, one or more functional groups F_(x) that are complementary toreactive group R_(x).

The exact identities of R_(x) and F_(x) will depend upon the nature ofthe desired covalent linkage and the chemistry used to form the covalentlinkage. Generally, reactive group R_(x) is a functional group that iscapable of reacting with a complementary functional group F_(x) underspecified reaction conditions to form a covalent linkage. However, thoseof skill in the art will recognize that a variety of functional groupsthat are typically unreactive under certain reaction conditions can beactivated to become reactive. Groups that can be activated to becomereactive include, e.g., carboxylic acids and esters, including saltsthereof. Such groups are referred to herein as “activatable precursors”and are specifically intended to be included within the expression“reactive group.”

Pairs of reactive groups R_(x) and complementary groups F_(x) suitablefor forming covalent linkages with one another under a variety ofdifferent reaction conditions are well-known. Any of these complementarypairs of groups can be used to covalently conjugate the dyes of theinvention to other compounds or substances. In one convenientembodiment, reactive group R_(x) and complementary functional groupF_(x) comprise complementary electrophiles and nucleophiles (or theirrespective activatable precursors). In another convenient embodiment,reactive group R_(x) is a photoactivatable group that becomes chemicallyreactive only after illumination with light of an appropriate wavelengthand complementary functional group F_(x) is a group capable of forming acovalent linkage with the chemically reactive species. Suchphotoactivatable groups can be conveniently used to photo cross-link thedyes of the invention to other molecules and/or substances.

A plethora of complementary electrophile/nucleophile pairs andphotoactivatable groups suitable for covalently conjugating twomolecules together are well-known. The actual choice of complementarypairs and/or photoactivatable group will depend upon a variety offactors, and will be apparent to those of skill in the art. Examples ofcomplementary electrophiles and nucleophiles suitable for use in a widevariety of contexts are shown in TABLE 2, where reaction between theindicated electrophilic and nucleophilic species yields the indicatedcovalent linkage. Conditions under which the covalent linkages may beformed are well-known. TABLE 2 Examples of Some Routes to UsefulCovalent Linkages Electrophilic Group Nucleophilic Group ResultingLinkage activated esters amines/anilines carboxamides acyl azides*amines/anilines carboxamides acyl halides amines/anilines carboxamidesacyl halides alcohols/phenols esters acyl nitriles alcohols/phenolsesters acyl nitriles amines/anilines carboxamides aldehydesamines/anilines imines aldehydes or ketones hydrazines hydrazonesaldehydes or ketones hydroxylamines oximes alkyl halides carboxylicacids esters acyl halides amines/anilines amides acyl halides alcoholsesters acyl halides thiols thioesters alkyl halides thiols thioestersalkyl sulfonylhalides amines alkyl sulfonamides alkyl sulfonylhalidesalcohols/phenols alkyl sulfonates anhydrides amines/anilinescarboxamides aryl halides thiols thiophenols aryl halides amines arylamines aziridines thiols thioethers boronates glycols boronate esterscarboxylic acids amines/anilines carboxamides carboxylic acids alcoholsesters carboxylic acids hydrazines hydrazides carbodiimides carboxylicacids N-acylureas or anhydrides diazoalkanes carboxylic acids estersepoxides thiols thioethers haloacetamides thiols thioethershalotriazines amines/anilines aminotriazines halotriazinesalcohols/phenols triazinyl ethers imido esters amines/anilines amidinesisocyanates amines/anilines ureas isocyanates alcohols/phenols urethanesisothiocyanates amines/anilines thioureas maleimides thiols thioethersphosphoramidites alcohols phosphite esters silyl halides alcohols silylethers sulfonate esters amines/anilines alkyl amines sulfonate estersthiols thioethers sulfonate esters carboxylic acids esters sulfonateesters alcohols ethers sulfonyl halides amines/anilines sulfonamidessulfonyl halides phenols/alcohols sulfonate esters*Acyl azides can rearrange to isocyanates.

As understood in the art, the “activated esters” of TABLE 2 generallyhave the formula —C(O)Ω, where Ω is a good leaving group. Exemplary goodleaving groups include, by way of example and not limitation:oxysuccinimidyl; N-succinimidyl; oxysulfosuccinimidyl;1-oxybenzotriazolyl; and —OR^(a), where R^(a) is selected from the groupconsisting of (C₄-C₂₀) cycloalkyl (e.g., cyclohexyl), 4-20 memberedheterocycloalkyl, (C₅-C₂₀) aryl, (C₅-C₂₀) aryl substituted with one ormore of the same or different electron-withdrawing groups (e.g., —NO₂,—F, —Cl, —CN, —CF₃, etc.), 5-20 membered heteroaryl, 5-20 memberedheteroaryl substituted with one or more of the same or differentelectron-withdrawing groups, n-dialkylaminoalkyls (e.g.,3-dimethylaminopropyl) and N-morpholinomethyl, or R^(a) is used to forman anhydride of the formula —OCOR^(b) or —OCNR^(b)NHR^(c), where R^(b)and R^(c) are each independently selected form the group consisting of(C₁-C₆) alkyl, (C₁-C₆) perhaloalky, (C₁-C₆) perfluoroalky and (C₁-C₆)alkoxy. A preferred activated ester is NHS ester.

Exemplary photoactivatable groups suitable for conjugation vialight-activated cross-linking include, but are not limited to, azido(—N₃), 4-azido-phenyl and 2-nitro-4-azido-phenyl. Conjugation usingphotoactivatable groups typically involves illuminating a mixturecomprising the photoactivatable dyes and the molecule or substance to beconjugated, followed by separation of unreacted dyes and byproducts.

As will be recognized by those of skill in the art, reactive group R_(x)can comprise any of the electrophilic, nucleophilic or photoactivatablegroups discussed above. The selection of reactive group R_(x) used tocovalently conjugate the dyes of the invention to the other molecule orsubstance typically depends upon the identity of the complementaryfunctional group F_(x) on the molecule or substance to be conjugated.The types of complementary functional groups typically present onmolecules or substances to be conjugated include, but are not limitedto, amines, thiols, alcohols, phenols, aldehydes, ketones, phosphates,imidazoles, hydrazines, hydroxylamines, mono- and disubstituted amines,halides, epoxides, sulfonate esters, carboxylic acids or carboxylates,or a combination of these groups. A single type of complementaryfunctional group may be available on the molecule or substance (which istypical for polysaccharides), or a variety of different complementaryfunctional groups may be available (e.g. amines, thiols, alcohols,phenols), which is typical for proteins. The molecule or substance maybe conjugated to more than one dye, which may be the same or differentAlthough some selectivity can be obtained by carefully controlling thereaction conditions, selectivity of conjugation is best obtained byappropriate choice of reactive group R_(x) in light of the availablecomplementary functional group(s) F_(x). In instances where the moleculeor substance to be conjugated does not contain available complementaryfunctional group(s) F_(x), it can be modified to contain such groupsusing any of a variety of standard techniques.

In a preferred embodiment, reactive group R_(x) is a group that reactswith, or that can be readily activated to react with, an amine, a thiolor an alcohol. A preferred reactive group R_(x) capable of reacting witha hydroxyl is a phosphoramidite. A preferred reactive group R_(x)capable of reacting with an amine is a carboxylic acid or an activatedester, most preferably a N-hydroxysuccinimidyl (NHS) ester. The NHSester may be conveniently obtained by reacting a dye of the inventionincluding a carboxylic acid reactive group R_(x) withN-hydroxysuccinimide in the presence of an activating agent (e.g.,dicyclohexylcarbodiimide) according to known methods. The preparation ofdyes having phosphoramidite reactive groups are described in a latersection.

For a discussion of the various reactive groups R_(x) and respectivecomplementary functional groups F_(x) that can be conveniently used tocovalently conjugate the dyes of the invention to a variety ofbiological and other molecules or substances, as well as reactionconditions under which the conjugation reactions can be carried out, seeHaugland, 1996, Molecular Probes Handbook of Fluorescent Probes andResearch Chemicals, Molecular Probes, Inc.; Brinkley, 1992, BioconjugateChem. 3:2 and Garman, 1997, Non-Radioactive Labelling: A PracticalApproach, Academic Press, London, as well as the references cited in allof the above. Additional suitable groups can be found in U.S. Pat. No.5,268,486 (see, e.g., Col. 15-17).

The mobility-modifying dyes of the invention will now be furtherdescribed by reference to various preferred embodiments. According toone preferred embodiment of the invention, the mobility-modifyingcyanine dyes are compounds according to structural formula (I.A):

-   -   wherein:        -   R¹, R², R³, R⁴, R⁵, R⁶, and R⁷ are each independently            selected from the group consisting of hydrogen, halogen, —F,            —Cl, —CN, —CF₃, (C₁-C₆) alkyl, (C₅-C₁₄) aryl or 5-14            membered heteroaryl;    -   k is an integer from 0 to 1;    -   l is an integer from 0 to 1;    -   m is an integer from 0 to 1;    -   Z is selected from the group consisting of —S—, —O—, —Se— and        —CR⁸R⁹—, where R⁸ and R⁹ when taken alone, are each        independently (C₁-C₆) alkyl, or when taken together are (C₄-C₅)        alkyleno or (C₄-C₅) alkano;    -   Z′ is selected from the group consisting of —S—, —O—, —Se— and        —CR⁸R⁹, where R⁸ and R⁹′, when taken alone, are each        independently (C₁-C₆) alkyl, or when taken together are (C₄-C₅)        alkyleno or (C₄-C₅) alkano;    -   L and R_(x) are a linker and a reactive group, respectively, as        previously described;    -   MM is a mobility-modifying moiety as previously described;    -   R¹¹, R¹², R¹³, R¹⁴, R¹⁹, R²⁰, R²¹ and R²², when taken alone, are        each independently selected from the group consisting of        hydrogen, (C₁-C₆) alkyl, (C₁-C₆) alkyl independently substituted        with one or more W, 2-6 membered heteroalkyl, 2-6 membered        heteroalkyl independently substituted with one or more W,        (C₅-C₁₀) aryl, (C₅-C₀) aryl independently substituted with one        or more W, (C₅-C₆) arylaryl, (C₅-C₆) arylaryl independently        substituted with one or more W, (C₆-C₁₆) arylalkyl, (C₆-C₁₆)        independently substituted with one or more W, 6-16 membered        arylheteroalkyl, 6-16 membered arylheteroalkyl independently        substituted with one or more W, 5-10 membered heteroaryl, 5-10        membered heteroaryl independently substituted with one or more        W, 5-6 membered heteroaryl-heteroaryl, 5-6 membered heteroaryl        independently substituted with one or more W, 6-16 membered        heteroarylalkyl, 6-16 membered heteroarylalkyl independently        substituted with one or more W, 6-16 membered        heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkyl        independently substituted with one or more W,    -   or when taken together with an adjacent R_(n) are each        independently selected from the group consisting of (C₆-C₁₀)        aryleno, (C₆-C₁₀) aryleno independently substituted with one or        more W, 6-10 membered heteroaryleno and 6-10 membered        heteroaryleno independently substituted with one or more W;    -   each W is independently —R, —X, ═O, —OR, ═S, —SR, —NRR, =NR,        (C₁-C₆) perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO, —NO₂, =N₂,        —N₃, —NHOH, —S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′,        —C(O)SR′, —C(S)SR′, and —C(NR)NRR;    -   each X is independently a halogen (preferably —F, —Cl or —Br);    -   each R is independently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆)        alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl,        (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl, 5-10 membered heteroaryl or        6-16 membered heteroarylalkyl;    -   each R′ is independently (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)        alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl,        5-10 membered heteroaryl or 6-16 membered heteroarylalkyl; and        -   each R″ is independently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl,            (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10            membered heteroaryl or 6-16 membered heteroarylalkyl. The            various R, R′ and R″ groups can be further substituted with            one or more of the same or different W groups, as defined            above.

One class of particularly preferred dyes according to structural formula(I.A) includes those compounds in which L, R_(x) and mobility-modifyingmoiety MM constitute one of their respective previously-describedpreferred embodiments.

Another class of particularly preferred dyes according to structuralformula (I.A) includes those compounds in which R¹, R², R³, R⁴, R⁵, R⁶,and R⁷ are each hydrogen and/or the sum of k, l and m is 2.

Still another class of particularly preferred dyes according tostructural formula (I.A) includes those compounds in which Z and Z′ arethe same; R²⁰ and R¹³ are the same; R²¹ and R¹² are the same; and/or R²²and R¹¹ are the same.

Yet another class of particularly preferred dyes according to structuralformula (I.A) includes those compounds in which any arylenos formed bytaking two adjacent R^(n) together are each independently benzo or benzosubstituted with one or more of the same or different strong anionicsubstituents.

Yet another class of particularly preferred dyes according to structuralformula (I.A) includes those compounds in which Z is —CR⁸R⁹—, where R⁸is (C₁-C₃) alkanyl and R⁹ is (C₁-C₃) alkanyl; and Z′ is —CR⁸, R⁹, whereR⁸ is (C₁-C₃) alkanyl and R⁹ is (C₁-C₃) alkanyl. Even more preferred arethose compounds in which Z and Z′ are the same, especially dyes in whichR⁸, R⁸, R⁹, R^(9′) are the same.

Yet another class of particularly preferred compounds according tostructural formula (I.A) includes compounds according to structuralformulae (I.D), (I.E), (I.F), (I.G), (I.H), (I.I), (I.J) and (I.K):

-   -   wherein:        -   R¹¹, R¹², R¹³, R¹⁴, R¹⁹, R²⁰, R²¹, R²², R³⁰, R³¹, R³², R³³,            R³⁴, R³⁵, R³⁶ and R³⁷ are each independently selected from            the group consisting of hydrogen, —S(O)₂O⁻ and —O—S(O)₂O⁻.

Especially preferred amongst the compounds of the structural formulae(I.D), (I.E), (I.F), (I.G), (I.H), (I.I), (I.J) and/or (I.K) are thosecompounds in which R¹¹, R¹², R¹³, R¹⁴, R¹⁹, R²⁰, R²¹, R²², R³⁰, R³¹,R³², R³³, R³⁴, R³⁵, R³⁶ and R³⁷ are each hydrogen.

A particularly preferred class of mobility-modifying dyes according tostructural formulae (I.D) and/or (I.H) are those compounds in which oneor two of R¹¹, R¹², R¹³ and R¹⁴ and/or one or two of R¹⁹, R²⁰, R²¹ andR²², are each independently —S(O)₂O⁻ or —O—S(O)₂O⁻; and the remaining Rsare each hydrogen.

A particularly preferred class of mobility-modifying dyes according tostructural formulae (I.E) and/or (I.I) are compounds in which R¹¹, R¹²,R²¹ and R²² are each hydrogen; one or two of R³⁰, R³¹, R³² and R³³and/or one or two of R³⁴, R³⁵, R³⁶ and R³⁷ are each independently—S(O)₂O⁻ or —O—S(O)₂O⁻; and the remaining Rs are each hydrogen.

A particularly preferred class of mobility-modifying dyes according tostructural formulae (I.F) and/or (I.J) are compounds in which R¹¹ andR¹² are each hydrogen; one or two of R³⁰, R³¹, R³² and R³³ and/or one ortwo of R¹⁹, R²⁰, R²¹ and R²² are each independently —S(O)₂O⁻ or—O—S(O)₂O⁻; and the remaining Rs are each hydrogen.

A particularly preferred class of mobility-modifying dyes according tostructural formulae (I.G) and/or (I.K) are compounds in which R²¹ andR²² are each hydrogen; one or two of R¹¹, R¹², R¹³ and R¹⁴ and/or one ortwo of R³⁴, R³⁵, R³⁶ and R³⁷ are each independently —S(O)₂O⁻ or—O—S(O)₂O⁻; and the remaining Rs are each hydrogen.

Representative exemplary preferred dyes according to structural formulae(I.D), (I.E), (I.F) and/or (I.G) are provided in the Examples section.The corresponding dyes according to structural formulae (I.H), (I.I),(I.J) and/or (I.K) are also preferred.

Those of skill in the art will appreciate that the various compoundsencompassed by formulae (I), (I.A), (I.D), (I.E), (I.F), (I.G), (I.H),(I.I), (I.J) and (I.K), as well as their various conjugates and reagentsdescribed infra, may exhibit the phenomenon of tautomerism. Depending onthe various substituents, many of these compounds also contain chiralcenters. The various compounds may further exhibit the phenomena ofconformational isomerism or geometric isomerism. As the formulaedrawings within this specification can represent only one of thepossible tautomeric, enantiomeric, conformational isomeric or geometricisomeric forms, it should be understood that the invention encompassesany tautomeric, enantiomeric, conformational isomeric or geometricisomeric forms of the compounds which exhibit the desired activitiesand/or properties described herein.

Moreover, all of the mobility-modifying cyanine dye compounds describedherein, and consequently their respective conjugates and reagents,include charged groups. It is to be understood that all of the compoundsdescribed herein include any necessary counterions, even though notexplicitly illustrated. Typical negatively charged counter ions tobalance the heteroaromatic imminium nitrogen and/or positively chargedsubstituents composing mobility-modifying moiety MM include, but are notlimited to, chloride, bromide, iodide, sulfate, alkanesulfonate,alkenesulfonate, alkynesulfonte, arylsulfonate, phosphate, perchlorate,periodate, tetrafluoroborate, tetrarylborate, nitrate and anions ofaromatic or aliphatic carboxylic acids. Typical positively chargedcounter ions to balance anionic substituents on the mobility-modifyingmoiety include, but are not limited to Na⁺, K⁺, Li⁺, quaternaryammoniums, etc. Counter ions suitable for balancing other substituentswill depend upon the charge of the substituent, and will be apparent tothose having skill in the art.

5.4 Methods of Synthesis

The synthetic route to the mobility-modifying cyanine dyes of theinvention requires the synthesis of three precursors: (i) a parentbenzazolium ring system E having a mobility-modifying moiety MM attachedto the benzazolium ring nitrogen; (ii) a parent benzazolium ring systemA having a linking moiety (-L-LG) attached to the benzazolium ringnitrogen; and (iii) a source for the bridge linking rings A and E. Whilethe mobility-modifying dyes of the invention have not been previouslydescribed, the chemistry that is required to prepare and combine theseprecursors so as to yield any of the compounds described herein isgenerally well-understood by one skilled in the art.

For example, methods suitable for synthesizing benzazolium precursorsaccording to structural formulae (A.1) and (E.1) are described in U.S.Pat. No. 5,436,134 (particularly at Cols. 13-33):

Additional suitable methods are described in U.S. Pat. Nos. 5,863,753;5,321,130; 5,410,030; 5,534,416; 5,582,977 and 5,658,751, as well as thevarious references cited therein.

In structural formulae (A.1) and (E.1), MM, L, R_(x), Z, Z′, R¹¹, R¹²,R¹³, R¹⁴, R¹⁹, R²⁰, R²¹ and R²² are as previously defined for structuralformula (I.A) and R⁴⁰ and R⁴⁰ are substituents whose nature isdetermined by the synthetic method utilized to couple the benzazoliumprecursor with each other. When the bridge joining the two heterocyclesis a methine bridge, then one of R⁴⁰ and R^(40′) is alkylthio (commonlymethylthio), chloro, bromo, or iodo and the other one of R⁴⁰ and R⁴⁰′ ismethyl. The methyl is incorporated into the final compound.

Compounds in which the heterocycles are joined by a polymethine bridgeaccording to structural formula (B. 1) or a cyclic alkylene bridgeaccording to structural formula (B.2) may be synthesized by methods thatare well-known in the art. Preferred methods of synthesis, exemplifiedwith certain preferred mobility-modifying dyes including a linkingmoiety of the formula -L-R_(x) and a polymethine bridge are outlined inSchemes (I) and (II), below. The various steps can be adapted asnecessary to synthesize the full range of mobility-modifying dyesaccording to the invention.

In Schemes (I) and (II), n, R²⁴, R²⁵, R²⁶, R²⁷ and R²⁸ are as previouslydefined for structural formula (MM.1); Z, Z′, L, R_(x), R¹¹, R¹², R¹³,R¹⁴, R¹⁹, R²⁰, R²¹ and R²² are as previously defined for structuralformula (I.A); Ph is phenyl; Ac₂O is acetic anhydride; Ac is acetate;and EtOH is ethanol.

Referring to Scheme (I), benzazolium precursor 5 is obtained by reducingan aldehyde precursor of the desired mobility modifying moiety 1 to itscorresponding alcohol 2 in the presence of a reducing agent such assodium borohydride. Alcohol 2 is then treated with HBr to yield thecorresponding bromide 3. Bromide 3 is reacted with benzazole 4 innitrobenzene solvent under argon atmosphere and 190° C. to yield thecorresponding mobility-modifying precursor 5. Compounds 1 are eithercommercially available or can be prepared using well-known techniques.

Schemes for synthesizing certain exemplary aromatic precursors 3 andanalogous aliphatic precursors useful for mobility-modifying benzazolering 11 to yield mobility-modified cyanine precursor 12 according toScheme (I) are illustrated in Schemes (Ia) and (Ib), respectively,below.

Referring to Scheme (Ia), commercially available aldehyde 41 is reducedto the alcohol with sodium borohydride in water, yielding the benzylalcohol 42, which upon treatment with hydrogen bromide and a metalbromide salt, yields the benzylic bromide 43. Benzylic bromide 43 can beused to functionalize the indolinine precursor to the cyanine dye withthe disulfonate mobility modifier according to Scheme (I), or can beused as a starting material to increase the length of the linkagebetween the sulfonated aromatic ring and the indolinine nitrogen. Asexamples, 43 can be carbonylated with carbon monoxide and hydrogen witha palladium catalyst to yield aldehyde 44; reduction of 44 to thealcohol 45 with lithium aluminum hydride, followed by treatment of 45with hydrobromic acid with lithium bromide yields the bromide 46 whichcan be used to functionalize the indolinine precursor to the cyanine dyeaccording to Scheme (I) with an ethyl linker between the aromaticdisulfonate and the indolinine nitrogen. In addition, 43 can becondensed with the sodium salt of dimethylmalonate to yield the dimethylester 47; hydrolysis of the ester to the bis-acid, which isdecarboxylated to the mono-acid with heat, followed by isolation work-upwith hydrochloric acid yields the free acid 48; reduction of 48 withlithium aluminum hydride to yield alcohol 49, followed by treatment of49 with hydrobromic acid with lithium bromide yields the bromide 50which can be used to functionalize the indolinine precursor to thecyanine dye according to Scheme (I) with a propyl linker between thearomatic disulfonate and the indolinine nitrogen.

Referring to Scheme (Ib), commercially available propandiol bromide 51can be converted to bromopropane disulfate 52, and propandiols 53(synthesized according to Serves et al., 1995, Phosphorous, SulfurSilicon Relat. Elem 101:75-82) and 55 (synthesized according to Ni andMatile, 1998, Chem. Commun. pp. 755-56) can be converted to bromopropanedisulfates 54 and 56, respectively, by treatment of the diols withsulfur trioxide, according to standard procedures (see, e.g, EverettGilbert, “Sulfonation and Related Reactions,” Robert E. KriegerPublishing Co, Huntington, N.Y., 1977, Chapter 6). Bromodisulfates 52,54, and 56 can be used to functionalize the indolinine cyanine dyeprecursor with the disulfate mobility modifier according to Scheme (I)to yield disulfates with methyl, ethyl, and bromo linkers, respectively,between the indolinine nitrogen and the disulfate portion of the chain.

The various precursors of the mobility-modifying dye are then condensedto form the completed dye, as illustrated in Scheme (II), supra.Referring to Scheme (II), bridge precursor 7 is reacted withmobility-modifying precursor 5 in the presence excess anhydride andheated to reflux (typically about 120 to 140° C.) to yield compound 8.Compound 8 is then condensed with benzazolium 6 (which is synthesizedaccording to Scheme (I) or standard methods) in the presence of a baseand a polar solvent to yield mobility-modifying dye 9.

Those of skill in the art will recognize that while Scheme II depicts aspecific bridge precursor 7, analogous precursors can be used to createmobility-modifying cyanine dyes containing different bridges using, forexample, the methods described in U.S. Pat. Nos. 5,436,134, 5,863,753,5,321,130, 5,410,030, 5,534,416, 5,582,977 and 5,658,751, as well as thevarious references cited therein. In addition, depending upon the natureof the Z, Z′, L, R_(x) and/or the various R substituents, these groupsmay require protection during all or some of the synthesis steps, and/orreaction with activating groups for further derivatization of the dye.Groups suitable for protecting and/or activating specificfunctionalities, as well as methods for their removal, are well-knownand will be apparent to those of skill in the art. Guidance forselecting suitable protecting groups can be found, for example, inGreene & Wuts, 1991, Protective Groups in Organic Synthesis, 2^(nd) Ed.,John Wiley & Sons, Inc., New York.

A significant advantage of Schemes (I) and (II) is that —S(O)₂O⁻ and—O—S(O)₂O⁻ groups on either mobility-modifier or the parentheteroaromatic rings are not reactive under the conditions used, andtherefore do not require protection. In addition, when reactive groupR_(x) is a carboxyl or a salt thereof, it does not require protectionduring the synthesis conditions outlined in Scheme (II). Thus, Schemes(I) and (II) are the preferred method of synthesizing compoundsaccording to structural formulae (I.D), (I.E), (I.F), (I.G), (I.H),(I.I), (I.J) and (I.K).

5.5 Reagents and Conjugates Incorporating the Dye Compounds

In another aspect, the present invention comprises reagents labeled orconjugated with the mobility-modifying cyanine dyes of the invention.Reagents of the invention can be virtually any molecule or substance towhich the dyes of the invention can be conjugated, including by way ofexample and not limitation, proteins, polypeptides, polysaccharides,nucleosides, nucleotides, polynucleotides, lipids, solid supports,organic and inorganic polymers, and combinations and assemblagesthereof, such as chromosomes, nuclei, living cells (e.g., bacteria orother microorganisms, mammalian cells, tissues, etc.), and the like. Thedyes are conjugated with the reagent via the linking moiety by a varietyof means, including hydrophobic attraction, ionic attraction, covalentattachment or with the aid of pairs of specific binding molecules, aspreviously described. Preferably, the dyes are conjugated via covalentattachment.

Conjugation typically results from mixing appropriate reactivemobility-modifying cyanine dyes and the molecules or substances to beconjugated in a suitable solvent in which both are soluble using methodswell-known in the art, followed by separation of the conjugate from anyunconjugated starting materials or unwanted by-products. The dyeconjugate can be stored dry or in solution for later use.

5.5.1. Nucleoside/Tide Reagents

A preferred class of conjugates include nucleosides/tides andnucleoside/tide analogs that are labeled with the dyes of the invention.Such labeled nucleosides/tides are particularly useful for labelingpolynucleotides formed by enzymatic synthesis, e.g., labeled nucleotidetriphosphates used in the context of template-directed primer extension,PCR amplification, Sanger-type polynucleotide sequencing, and/ornick-translation reactions. Referring to Scheme (III), below,dye-labeled nucleoside/tides and/or nuleoside/tide analog conjugates aregenerally obtained by condensing a nucleoside/tide or nucleoside/tideanalog modified to contain a linking moiety of the formula -L-F_(x) (35)with a dye according to structural formula (I.A) in which LG is areactive group R_(x) (36) to yield a dye-labeled nucleosides/tides ornucleoside/tide analog according to structural formula (II).

In Scheme (III), L and R_(x), are a linker and a reactive group,respectively, as previously described; D represents a mobility-modifyingdye chromophore; F_(x) is complementary functional group, as previouslydescribed; L′ is a bond or a second linker; NUC represents anucleoside/tide or a nucleoside/tide analog; and R⁴¹ represents acovalent linkage formed by reaction between R_(x) and F_(x), as will bedescribed in more detail, below.

During the condensation, reactive group R_(x) and complementaryfunctional group F_(x) react to form covalent linkage R⁴¹. Thus, it willbe recognized by those of skill in the art that reactive group R_(x) andcomplementary functional group F_(x) can each constitute respectivemembers of the various pairs of complementary groups described supra,such as the various pairs of complementary electrophiles andnucleophiles listed in TABLE 2. Preferably, one of R_(x) or F_(x)(preferably F_(x)) is an amine, thiol or hydroxyl group, most preferablya primary amine group, and the other one of R_(x) or F_(x) (preferablyR_(x)) is a group capable of reacting with an amine, thiol or hydroxyl,most preferably a carboxylic acid or a salt, ester or activated esterthereof. Thus, a particularly preferred covalent linkage R⁴¹ is an amideof the formula —C(O)NR⁴⁵—, where R⁴⁵ is hydrogen or (C₁-C₆) alkyl.

Complementary functional group F_(x) is attached to NUC via linker L′.Complementary functional group F_(x) may be attached directly to NUC, inwhich case L′ represents a bond, or it may be spaced away from NUC byone or more intervening atoms, in which case L′ represents a linker. Anyof the linkers L previously described in connection with themobility-modifying cyanine dyes per se can be used for linker L′.Preferred linkers L′ are described in more detail below.

Complementary functional group F_(x) may be attached to NUC at a varietyof different positions, e.g., the nucleobase, the sugar and/or thephosphate ester or other backbone moiety. Nucleosides/tides andnucleoside/tide analogs that are appropriately modified at these variouspositions such that they can be conjugated with dye pairs according tothe invention are known in the art. Preferably, complementary groupF_(x) is attached to the nucleobase via linker L′. When the nucleobaseis a 7-deazapurine, L′ is usually attached to the C7 or C8 position ofthe nucleobase. When the nucleobase is a pyrimidine, L′ is usuallyattached to the C5 position of the nucleobase. When the nucleobase is apurine, L′ is usually attached to the C7 position of the nucleobase.Linkers L′ useful for covalently conjugating the dyes of the inventionto the nucleobase of NUC are described in U.S. Pat. No. 5,821,356, U.S.Pat. No. 5,770,716 and U.S. application Ser. No. 08/833,854 filed Apr.10, 1997, the disclosures of which are incorporated herein by reference.

Preferred linkers L′ for covalently conjugating the dyes of theinvention to the nucleobase of NUC include (C₁-C₂₀) alkylenos, 2-20membered heteroalkyldiyls and 2-20 membered heteroalkylenos, especially(C₁-C₂₀) alkynos, (C₁-C₂₀) alkenos, 2-20 membered heteroalkynos and 2-20membered heteroalkenos. A particularly preferred linker L′ is —C≡C—CH₂—,where the terminal sp carbon is covalently attached to the nucleobase ofNUC and the terminal methylene (sp³) carbon is covalently attached toR⁴¹ in the compounds of structural formula (II), or to F_(x) of compound35.

Additional preferred linkers L′ for covalently conjugating the dyes orof the invention to the nucleobase of NUC include propargylethoxy groupsaccording to structural formula —C≡C—CH₂—O—CH₂—CH₂—NR⁴⁷—R⁴⁸—, whereinR⁴⁷ is hydrogen or (C₁-C₆) alkyl and R⁴⁸ is selected from the groupconsisting of —C(OHCH₂)_(r)—, —C(O)—CHR⁴⁹—, —C(O)—C═C—CH₂— and—C(O)-φ-CH₂)_(r)—, where each r is independently an integer from 1 to 5and φ represents a C₆ aryldiyl or a 6-membered heteroaryldiyl,preferably phena-1,4-diyl

and R⁴⁹ is hydrogen, (C₁-C₆) alkyl or an amino acid side chain(including side chains of both gene-encoded and non-encoded aminoacids). With these linkers L′, the terminal sp carbon is attached to thenucleobase of NUC and the other terminal group is attached to R⁴¹ in thecompounds of structural formula (II), or to F_(x) of compound 35.

In a preferred embodiment, the labeled nucleosides/tide and/ornucleoside/tide analogs according to structural formula (II) are labeledenzymatically-incorporable nucleotides, labeled enzymatically extendiblenucleotides or labeled terminators.

In another preferred embodiment, the labeled nucleosides/tides andnucleoside/tide analogs are those obtained from Scheme (III) in whichcompound 36 is a compound according to structural formula (I.A), (I.D),(I.E), (I.F), (I.G), (I.H), (I.I), (I.J) or (I.K), or any of thepreferred embodiments thereof and/or compound 35 is a compound accordingto structural formula (IIa):

-   -   wherein:        -   B is a nucleobase;        -   F_(x) is a complementary functional group as previously            described;        -   L′is a linker a previously described;        -   R⁷⁰ and R⁷¹, when taken alone, are each independently            selected from the group consisting of hydrogen, hydroxyl and            a moiety which blocks polymerase-mediated template-directed            polymerization, or when taken together form a bond such that            the illustrated sugar is 2′,3′-didehydroribose; and        -   R⁷² is selected from the group consisting of hydroxyl, a            phosphate ester having the formula            where α is an integer from 0 to 2, and a phosphate ester            analog. Typically, F_(x) is an amino group of the formula            —NHR⁵¹, where R⁵¹ is hydrogen or (C₁-C₆)alkyl, but can be            any of the nucleophilic or electrophilic groups listed in            TABLE 2, supra.

In a preferred embodiment of structural formula (IIa), B is a normalnucleobase or a common analog thereof, a 7-deazapurine, a purine or apyrimidine and L′ is one of its previously described preferredembodiments. In a particularly preferred embodiment, B is a nucleobaseselected from the group consisting of adenine, 7-deaza-adenine,cytosine, guanine, 7-deaza-guanine, thymine and uracil. When thepreferred nucleobase B is a purine or a 7-deaza-purine, the pentosemoiety is attached to the N⁹-position of the nucleobase, and when thepreferred B is a pyrimidine, the pentose moiety is attached to theN′-position of the nucleobase. Linker L′ is attached to nucleobase B aspreviously described.

In structural formula (IIa), when both R⁷⁰ and R⁷¹ are hydroxyl, theresultant compounds produced in Scheme (III) are labeledribonucleoside/tides. When R⁷⁰ is hydrogen and R⁷¹ is hydroxyl, theresultant compounds are labeled 2′-deoxyribonucleoside/tides. When R⁷⁰and R⁷¹ are each hydrogen, the resultant compounds are2′,3′-dideoxyribonucleoside/tides Labeled2′,3′-dideoxyribonucleoside-5′-triphosphates (ddNTPs) find particularuse as terminators in Sanger-type DNA sequencing methods utilizingfluorescent detection. Labeled 2′-deoxyribonucleoside-5′-triphosphates(dNTPs) find particular use as means for labeling DNA polymeraseextension products, e.g., in the polymerase chain reaction ornick-translation. Labeled ribonucleoside-5′-triphosphates (NTPs) findparticular use as means for labeling RNA polymerase extension products.

Referring to Scheme (III), supra, the synthesis ofalkynylamino-derivatized compounds 35 useful for conjugating the dyes ofthe invention to nucleosides/tides and/or nucloside/tide analogs istaught in EP 87305844.0 and Hobbs et al., 1989, J. Org. Chem. 54:3420.Briefly, the alkynylamino-derivatized nucleotides are formed by placingthe appropriate halonucleoside (usually 5-iodopyrimidine and7-iodo-7-deazapurine dideoxynucleosides as taught by Hobbs et al., 1989,supra) and Cu(I) in a flask, flushing the flask with argon to remove airand adding dry DMF followed by addition of an alkynylamine,triethylamine and Pd(0). The reaction mixture is stirred for severalhours, or until thin layer chromatography indicates consumption of thehalonucleoside. When an unprotected alkynylamine is used, thealkynylamino-nucleoside can be isolated by concentrating the reactionmixture and chromatographing on silica gel using an eluting solventwhich contains ammonium hydroxide to neutralize the hydrohalidegenerated in the coupling reaction. When a protected alkynylamine isused, methanol/methylene chloride can be added to the reaction mixture,followed by the bicarbonate form of a strongly basic anion exchangeresin. The slurry can then be stirred for about 45 minutes, filtered,and the resin rinsed with additional ethanol/methylene chloride. Thecombined filtrates can be concentrated and purified byflash-chromatography on silica gel using a methanol-methylene chloridegradient. The corresponding nucleoside mono-, di- and triphosphates areobtained by standard techniques (see, e.g., the methods described inU.S. Pat. No. 5,821,356, U.S. Pat. No. 5,770,716 and U.S. applicationSer. No. 08/833,854 filed Apr. 10, 1997, discussed supra). Methods forsynthesizing compound 35 modified with a propargylethoxyamido linker L′can also be found in these patents and application.

Additional synthesis procedures suitable for use in synthesizingcompounds according to structural formula (II) are described, forexample, in Gibson et al., 1987, Nucl. Acids Res. 15:6455-6467; Gebeyehuet al., 1987, Nucl. Acids Res. 15:4513-4535; Haralambidis et al., 1987,Nucl. Acids Res. 15:4856-4876; Nelson et al., 1986, Nucleosides andNucleotides. 5(3):233-241; Bergstrom et al., 1989, J. Am. Chem. Soc.111:374-375; U.S. Pat. No. 4,855,225, U.S. Pat. No. 5,231,191 and U.S.Pat. No. 5,449,767, the disclosures of which are incorporated herein byreference. Any of these methods can be routinely adapted or modified asnecessary to synthesize the full range of labeled nucleosides/tides andnucleoside/tide analogs described herein.

5.5.2. Phosphoramidite Reagents

Another preferred class of reagents of the invention comprisesphosphoramidite compounds which incorporate the mobility-modifyingcyanine dyes of the invention. Such phosphoramidite reagents areparticularly useful for the automated chemical synthesis ofpolynucleotides labeled with the dyes of the invention. Suchphosphoramidite reagents, when reacted with a hydroxyl group, such as a5′-hydroxyl group of a nucleoside/tide or polynucleotide, form aphosphite ester linkage which, in turn, is oxidized to yield a phosphateester linkage. For a detailed discussion of phosphoramidite chemistrysee, e.g., Caruthers et al., U.S. Pat. Nos. 4,458,066 and 4,415,732 andGait, 1985, Oligonucleotide Synthesis: A Practical Approach, IRL Press,Oxford, England. The phosphoramidite reagents can be nucleosidic ornon-nucleosidic, as will be described in more detail, below.

5.5.2.1 Non-Nucleosidic Phosphoramidite Reagents

In one aspect, the phosphoramidite reagents of the invention arenon-nucleosidic compounds according to structural formula (III):

-   -   wherein:        -   N, O and P represent nitrogen, oxygen and phosphorous,            respectively;        -   L″ represents a bond or a linker as will be described more            fully below;        -   R⁴¹ represents a bond or a linkage as previously defined for            structural formula (II);        -   L represents a linker as previously defined for structural            formula (I);        -   D represents a dye chromophore according to the invention or            a protected derivative thereof;        -   R⁶⁰ is a phosphite ester protecting group;        -   R⁶′, when taken alone, is selected from the group consisting            of (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆)            alkynyl, (C₃-C₁₀) cycloalkyl, (C₅-C₂₀) aryl and (C₆-C₂₆)            arylalkyl, or when taken together with R⁶² forms a            straight-chain or branched (C₂-C₀) alkyleno or a            straight-chain or branched 2-10 membered heteroalkyleno; and        -   R⁶², when taken alone, is selected from the group consisting            of (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆)            alkynyl, (C₃-C₁₀) cycloalkyl, (C₅-C₂₀) aryl and (C₆-C₂₆)            arylalkyl, or when taken together with R⁶¹ forms a            straight-chain or branched (C₂-C₀) alkyleno or a            straight-chain or branched 2-10 membered heteroalkyleno.

According to structural formula (III), R⁶⁰ is a phosphite esterprotecting group which prevents unwanted extension of the polynucleotideto which the phosphoramidite is attached. Generally, R⁶⁰ is stable topolynucleotide synthesis conditions yet is able to be removed from asynthetic polynucleotide product with a reagent that does not adverselyaffect the integrity of the polynucleotide or the dye. A variety ofphosphite ester groups having these characteristics are well-known inthe art. Preferably, R⁶⁰ is methyl, β-cyanoethyl or 4-nitrophenylethyl.

While not depicted in structural formula (III), dye chromophore D isattached to linker L at the heteroaromatic imminium nitrogen, asdepicted in structural formula (I). In some instances, D may containfunctional groups that require protection, either during the synthesisof the phosphoramidite reagent or during its subsequent use to labelmolecules such as polynucletodies. The protecting group(s) used willdepend upon the nature of the functional groups, and will be apparent tothose having skill in the art. Generally, the protecting groups usedshould be stable under the acidic conditions commonly employed inpolynucleotide synthesis to remove 5′-hydroxylprotecting groups (e.g.,dimethoxytrityl) and labile under the basic conditions used to deprotectand/or cleave synthetic polynucleotides from resins. Guidance forselecting appropriate protecting groups can be found, for example, inGreene & Wuts, 1991, Protective Groups in Organic Synthesis, John Wiley& Sons, Inc., New York.

It should be noted, however, that cyanine dyes are generally notcompletely stable under the basic conditions typically used to deprotectand/or cleave synthetic polynucleotides from synthesis resins. Thus, anybase-labile protecting groups used should be removable under relativelymild basic conditions (e.g., exposure to ammonium hydroxide or 0.05Mpotassium carbonate in methanol for 2 hrs. or less at a temperature of55° C. or less or, alternatively, exposure to a 50:50 mixture ofammonium hydroxide and 40% aqueous methylamine for 90 min. at roomtemperature or 5 min. 65° C.). Of course, any exocyclic amines or otherfunctionalities on the nucleoside phosphoramidites used to synthesizethe polynucleotide that will be labeled with the compounds according tostructural formula (III) should likewise be protected with such mildbase-labile protecting groups. Suitable groups are known in the art, andinclude, for example, isobutyryl, phenoxyacetyl,4-isopropyl-phenoxyacetyl and acetyl. Other protecting groups havingthese properties will be apparent to those having skill in the art.Polynucleotide synthesis reagents and supports having appropriatebase-labile linkage and protecting groups, as well as reagents for theirremoval and/or cleavage are commercially available (see, e.g., productscatalog of Glen Research, Sterling, Va. 20164).

The phosphoramidite portion of the molecule is linked to dye chromophoreD via linkage -L″-R^(4l)-L-. As will be discussed in more detail below,the linkage -L″-R⁴¹-L- can take a variety of forms, but generally mustbe a linkage that is (i) stable to DNA synthesis conditions; (ii) doesnot substantially interfere with oligonucleotide-target hybridization;and (iii) does not quench the fluorescence of the dye to which it isattached, e.g., U.S. Pat. Nos. 5,231,191, 5,258,538, 4,757,141 and5,212,304.

The composition of -L″-R⁴¹-L- is in part dictated by the methods used tosynthesize the phosphoramidite reagents. For example, appropriatelyprotected mobility-modifying dyes according to structural formula (I) inwhich linking group LG is a hydroxyl can be conveniently phosphitylatedusing standard methods and reagents to yield phosphoramidites accordingto structural formula (III). In these instances, L is any of thepreviously-described linkers that is compatible with polynucleotidesynthesis conditions and -L″-R⁴¹ constitutes a bond.

Alternatively, dyes of formula (I) in which linking moiety LG isreactive group R_(x) can be conveniently “converted” to include ahydroxyl by reacting the dye with an “adapter molecule” which includes ahydroxyl and a functional group complementary to reactive group R_(x),such as any of the previously-described complementary functional groupsF_(x) (see, e.g., TABLE 2, supra.). Analogous to the compounds ofstructural formula (II), in the compounds of structural formula (III),the reaction between reactive group R_(x) and functional group F_(x)form linkage R⁴¹. The oxygen intervening the phosphorous atom and linkerL″ is contributed by the adapter molecule. Thus, adapter moleculesuseful for providing a hydroxyl group suitable for phosphitylation aregenerally compounds having the structure R⁶³—O-L″-F_(x), where R⁶³ ishydrogen or a hydroxyl protecting group, preferably an acid-labilehydroxyl protecting group as described in more detail, infra.Preferably, F_(x) is an amine of the formula —NHR⁵⁶, where R⁵⁶ ishydrogen or (C₁-C₆) alkyl and reactive group R_(x) of the dye is acarboxyl or carboxylate, or an activated ester thereof, such that R⁴¹ inthe compounds of structural formula (III) is an amide or substitutedamide having the formula —NR⁵⁶—C(O)—, where R⁵⁶ is as previouslydescribed.

Linker L″ is analogous to linker L and therefore may be flexible orrigid, long or short, or hydrophobic or hydrophilic, depending upon theparticular application. Linker L″ can be any of the previously describedlinkers L or L′ that are stable to polynucleotide synthesis conditions.Selection of an appropriate linker will depend upon the particularapplication, and will be apparent to those having skill in the art. Forexample, linker L″ may be a (C₁-C₃₀) alkyldiyl, 1-30 memberedheteroalkyldiyl, (C₅-C₁₄) aryldiyl, (C₅-C₁₄) arylaryldiyl, (C₆-C₂₆)arylalkyldiyl, 6-26 membered arylheteroalkyldiyl, 5-14 memberedheteroaryldiyl, 5-14 membered heteroaryl-heteroaryldiyl, 6-26 memberedheteroarylalkyldiyl or 6-26 membered heteroaryl-heteroalkyldiyl.Preferred linkers L″ include alkylenos and heteroalkylenos, especially(C₁-C₃₀) alkanos and linear polyethylene oxides having the formula—(CH₂CH₂O)_(u)—CH₂CH₂—, where u is an integer ranging from 1 to 30,preferably from 2 to 10, and more preferably from 2 to 6.

Those of skill in the art will appreciate that compounds according tostructural formula (III) are particularly useful for labeling the5′-terminus of synthetic polynucleotides with the mobility-modifyingdyes of the invention. However, in many instances it may be desirable tolabel the 3′-terminus and/or to provide internal labels intervening thenucleosides of a synthetic polynucleotide. In these instances, linker L″(or, alternatively linker L) should provide a hydroxyl group forsubsequent synthesis. The hydroxyl for subsequent synthesis is protectedduring the phosphitylation reaction with an acid-labile protectinggroup, such as those typically used to protect the primary 5′-hydroxylof the 2′-deoxyribonucleoside phosphoramidites commonly employed inpolynucleotide synthesis, as described in more detail, infra. Preferredlinkers L″ (or alternatively L) according to this aspect of theinvention include branched (C₁-C₃₀) alkyls substituted with a hydroxyl.Particularly preferred phosphoramidite reagents according to this aspectof the invention are compounds according to structural formula (III.A):

-   -   wherein:        -   N, P and O represent nitrogen, phosphorous and oxygen,            respectively;        -   R⁴¹, L, D, R⁶⁰, R⁶¹ and R⁶² are as previously defined for            structural formula (III);        -   R⁶³ is hydrogen or an acid-labile hydroxyl protecting group;            and        -   v is an integer from 1 to 30, preferably from 1 to 5.

In the compounds of structural formula (III.A), R⁶³ is hydrogen or anacid labile hydroxyl protecting group. Preferably, R⁶³ is atriphenylmethyl (trityl) group or a derivative thereof that issubstituted with one or more of the same or different electron-donatingsubstituents. As used herein, the term “electron-donating” refers to thetendency of a substituent to release valence electrons to neighboringatoms in the molecule of which it is a part, i.e., it is electropositivewith respect to neighboring atoms. Preferably, electron-donatingsubstituents include amino, (C₁-C₆) alkyl, (C₁-C₈) aryl, (C₁-C₆) alkoxy,and the like. More preferably, the electron-donating substituent(s) aremethoxy. Exemplary acid-labile trityl derivatives include4,4′-dimethoxytrityl, i.e. bis(p-anisyl)phenylmethyl, monomethoxytrityl,α-naphthyldiphenylmethyl, tri(p-methoxyphenyl)methyl, and the like.Attachment and cleavage conditions for these and other trityls can befound in Greene and Wuts, 1991, Protective Groups in Organic Synthesis,2^(nd) Ed., John Wiley & Sons, New York, and Gait, 1985, OligonucleotideSynthesis: A Practical Approach, IRL Press, Oxford, England.

In a preferred embodiment of the invention, in the compounds ofstructural formulae (III) and (III.A), R⁶¹ and R⁶² are taken alone andare each independently a branched or straight-chain (C₁-C₆) alkyl, morepreferably a branched or straight-chain (C₁-C₆) alkanyl. In aparticularly preferred embodiment, R⁶¹ and R⁶² are each independentlypropan-2-yl (isopropyl), butan-2-yl, butan-3-yl, 2-methyl-propan-1-yl(iso-butyl) or 2-methyl-propan-2-yl (t-butyl).

In another preferred embodiment, in the compound of structural formulae(III) and (III.A), R⁶′ and R⁶² are taken together and form a straightchain (C₂-C₅) alkano bridge or a (C₂-C₁₀) branched alkano bridge inwhich the principle chain or bridge contains from 2 to 5 carbon atoms.In an alternative preferred embodiment, R⁶¹ and R⁶², when taken togetherwith the nitrogen atom, form a 5-8 membered heteroalkyl, optionallycontaining one or more additional heteroatoms selected from the groupconsisting of nitrogen, oxygen and sulfur. In a particularly preferredembodiment, R⁶¹ and R⁶², when taken together with the nitrogen atom,form a morpholino group.

In yet another preferred embodiment, in the compounds of structuralformulae (III) and (III.A), D is a chromophore derived from structure(I), (I.A), (I.D), (I.E), (I.F) or (I.G), or any of their preferredembodiments.

Phosphoramidite reagents according to structural formulae (III) and(III.A) can be synthesized by a variety of known methods. Hydroxyls andother reactive functionalities of the dye chromophore are protected withprotecting groups that can be removed under the desired conditions,commonly with a DNA synthesis deprotection agent, such as ammonia,ethanolamine, iodine, methylamine/ammonium hydroxide mixtures, andmixtures of t-butylamine/water/methanol (1:2:1) (see, e.g., U.S. Pat.No. 5,231,191). Preferred protecting groups include esters of benzoicacid or pivalic acid. Most preferably, the protecting groups areremovable under mildly basic conditions, as described supra.

Any hydroxyl groups on L, L′, or L″ for subsequent synthesis areprotected with an acid-labile protecting group, preferably4,4′-dimethoxytrityl, prior to phosphitylation. If linking moiety LG ofthe protected dye is a hydroxyl, it can be phosphitylated according tostandard methods. If the linking moiety contains reactive group R_(x),such as, for example, a carboxyl group, it is activated, e.g., withcarbodiimide, and reacted with an adapter molecule, e.g., ethanolamine,hexanol amine, or the like, in N,N-dimethylformamide (DMF), or anotherlike aprotic solvent to yield a protected dye with a hydroxylfunctionality. The hydroxyl is then reacted with a phosphitylating agentusing standard procedures, e.g.,di-(N,N-diisopropylamino)methoxyphosphine in acetonitrile containingcatalytic amounts of tetrazole diisopropylamine, to yield thephosphoramidite (see, e.g., U.S. Pat. No. 5,231,191).

5.5.2.2 Nucleosidic Phosphoramidite Reagents

In a second preferred embodiment, the phosphoramidite reagents of theinvention are 2′-deoxyribonucleoside-5′-phosphoramidites according tostructural formula (IV):

-   -   wherein:        -   B is a nucleobase or a protected derivative thereof;        -   L′, R⁴¹, L, D, R⁶⁰, R⁶¹ and R⁶² are as previously described            for structural formula (III); and        -   R⁶³ is as previously described for structural formula            (III.A).

When B is a purine or 7-deazapurine, the illustrated 2′-deoxyribosemoiety is attached to the N⁹-position of the purine or deazapurine.Alternatively, when B is a pyrimidine, the 2′-deoxyribose moiety isattached at the N¹-position of the pyrimidine. B and D are linkedthrough linkage -L′-R⁴¹-L-, typically formed by the reaction ofcomplementary reactive and functional groups, as described in detailabove. If B is a purine, L′ is attached to the C-8 position of thepurine, while if B is a 7-deazapurine, L′ is attached to the C-7position of the 7-deazapurine. If B is a pyrimidine, L′ is attached tothe C-5 position of the pyrimidine. The site of attachment of L′ toother nucleobases will be apparent to those of skill in the art.

As will be recognized by those of skill in the art, the exocyclic aminesand other functionalities of nucleobase B may require protection duringthe synthesis of the phosphoramidite reagent and/or during itssubsequent use to synthesize labeled polynucleotides. The particularprotecting group(s) selected will depend on the identity of thenucleobase or nucleobase analog, and will be apparent to those of skillin the art. Generally, protecting groups commonly used in the art ofnucleic acid synthesis are used. For example, the exocyclic amines ofadenine and cytosine can be protected with benzoyl (Bz) and theexocyclic amine of guanine can be protected with dimethylformamide (dmf)or isobutyryl (iBu) using conventional N-acylating procedures. The O⁶amide oxygen of guanine, as well as the O⁴ amide oxygen of thymineand/or uracil can also be optionally protected with, for example,phosphinothioyl, 2-nitrophenyl or substituted ethyl groups (e.g.,cyanoethyl) using conventional techniques (see, e.g., Deskalov et al.,1981, Bull. Chem. Soc. Japan 54:3076; Jones et al., 1981, TetrahedronLett. 22:4755; Gaffney & Jones, 1982, Tetrahedron Lett. 23:2257;Trichtinger et al., 1983, Tetrahedron Lett. 24:211; Himmelsbach et al.,1981, Tetrahedron Lett. 40:59).

Preferably, the nucleobase is protected with groups that are readilyremoved under mild basic conditions, as previously described. Protectinggroups removable under such mild basic conditions are well-known. Forexample, polynucleotides synthesized with dA^(Bz), dC_(Bz), dG^(iBu) anddT phosphoramidities (and their corresponding resins) can be cleaved anddeprotected in 90 minutes or less using a 50:50 mixture of ammoniumhydroxide and 40% aqueous methylamino (Aldrich M2, 775-1), dependingupon the temperature (5 minutes at 65° C.; 90 minutes at 25° C.).Polynucleotides synthesized with dA^(iBz), dA^(Pac), dC^(AC),dG^(iPr-Pac) and dT phosphoramidites (and their corresponding resins)can be cleaved and deprotected in 2 hours at room temperature withammonium hydroxide or 0.05M potassium carbonate in methanol. Thus,preferred exocyclic amine protecting groups for adenine are benzoyl(Bz), isobutyryl (iBu) and phenoxyacetyl (Pac). Preferred exocyclicamine protecting groups for cytosine are Bz and acetyl (Ac). Preferredexocyclic amine protecting groups for guanine are iBu and4-isopropyl-phenoxyacetyl (iPr-Pac). The actual protecting groupselected for a particular nucleobase will depend upon the protection ofthe other nucleobase and will be apparent to those of skill in the art.

Preferred compounds according to structural formula (IV) include thosecompounds in which L″ is one of the previously described preferredembodiments of linker L′ and L, D, R⁶⁰, R⁶¹, R⁶², and/or R⁶³ are theirrespective preferred embodiments previously described in connection withstructural formula (III) or (III.A).

The 2′-deoxyribonucleoside phosphoramidites according to structuralformula (IV) can be synthesized using standard methods, as isillustrated in Scheme (IV), below, with a propargyl linker L′, carboxylreactive groups R_(x) and primary amino complementary functional groupsF.

In Scheme (IV), R⁶⁰, R⁶¹, R⁶², R⁶³, B, L and D are as previously definedfor structural formula (IV) and B^(p) is a protected nucleobase ornucleobase analog.

According to Scheme (IV), nucleoside 60 is N-acylated to protect anyexocyclic amines using standard procedures, yielding protectednucleoside 61. Protected nucleoside 61 is reacted with chloride 62(e.g., 4,4′-dimethoxytritylchloride) to yield 5′-protected nucleoside63. Compound 63 is reacted with compound 64 in the presence ofpalladium(0), yielding protected propargyl linker-modified nucleoside65. The t-butylsilyl protecting group of the propargylamino linker isselectively removed with tetrabutyl ammonium fluoride (nBu₄N⁺F⁻) toyield protected nucleoside 66. Next, the protected nucleoside 66 islabeled with the dye by reacting it with dye 67 under conditions inwhich the reactive group of the dye react with the complementaryfunctional group of the protected nucleoside to form a covalent linkage.In the specific example illustrated in Scheme (IV), the reactivecarboxyl of dye 67 is conveniently converted to a reactive ester, e.g.,a NHS ester, with dicyclohexyl carbodiimide and N-hydroxysuccinimide.The activated NHS ester then reacts with compound 66 to yielddye-labeled nucleoside 68, which is phosphitylated with compound 69 toyield phosphoramidite 70. Any reactive groups on dye chromophore D orlinker L can be protected as previously described. Methods ofsynthesizing compounds according to structural formula (IV) includinglinkers L′ and linkages R₄₁ other than those depicted in Scheme (IV) canbe synthesized by routine modification of the above method, by resort toother conventional synthetic methods (see, e.g., Meyer, “Incorporationof Modified Bases into Oligonucleotides,” In: Methods in MolecularBiology Volume 26: Protocols for Oligonucleotide Conjugates, Chapter 2,Agarwal, Ed., 1994, Humana Press, Totowa, N.J., as well as thereferences cited therein), or by routine modification of the methodsprovided in connected with the compounds of structural formula (III).

Labeled 2′-deoxyribonucleoside-3′-phosphoramidites according tostructural formula (IV) are particularly well suited for providinglabels at the 3′, 5′ and/or internal positions of chemically-synthesizedpolynucleotides.

5.5.2.3 Polynucleotide Reagents

Yet another preferred class of reagents of the present inventioncomprise polynucleotides or polynucleotide analogs labeled with themobility-modifying cyanine dyes of the invention. Such labeledpolynucleotides or analogs are useful in a number of important contexts,including as DNA sequencing primers, PCR primers, oligonucleotidehybridization probes, oligonucleotide ligation probes, and the like.

In one preferred embodiment, the labeled polynucleotides orpolynucleotide analogs of the present invention include multiple dyespositioned so that fluorescence energy transfer takes place therebetween. Such multi-dye energy-transfer polynucleotides find applicationas spectrally-tunable sequencing primers as described, for example, inJu et al., 1995, Proc. Natl. Acad. Sci. USA 92:4347-4351, and ashybridization probes as described, for example, in Lee et al., 1993,Nucl. Acids Res. 21:3761-3766.

Labeled polynucleotides and/or polynucleotide analogs may be synthesizedeither enzymatically, e.g., using a DNA polymerase or ligase (see, e.g.,Stryer, 1981, Biochemistry, Chapter 24, W.H. Freeman and Company), or bychemical synthesis, e.g., by the phosphoramidite method, thephosphite-triester method, and the like (see, e.g., Gait, 1990,Oligonucleotide Synthesis, IRL Press, Oxford, England). Labels may beintroduced during enzymatic synthesis utilizing the labeledenzymatically-incorporable nucleoside/tides and/or nucleoside/tideanalogs described above, or during chemical synthesis using the labelednon-nucleosidic or nucleosidic phosphoramidite reagents described above.Alternatively, the labels may be introduced subsequent to synthesis viaconventional conjugation reactions.

Generally, if the labeled polynucleotide is made using enzymaticsynthesis, the following procedure may be used. A target DNA isdenatured and an oligonucleotide primer is annealed to the template DNA.A mixture of enzymatically-incorporable nucleoside/tides ornucleoside/tide analogs capable of supporting continuoustemplate-directed enzymatic extension of the primed target (e.g., amixture including dGTP, dATP, dCTP and dTTP or dUTP) is added to theprimed target. At least a fraction of the nucleoside/tides ornucleoside/tide analogs is labeled with a dye compound of the inventionor are labeled terminators, as described above. Next, a polymeraseenzyme is added to the mixture under conditions where the polymeraseenzyme is active. A labeled polynucleotide is formed by theincorporation of the labeled nucleoside/tides or nucleoside/tide analogsor terminators during polymerase-mediated strand synthesis. In analternative enzymatic synthesis method, two primers are used instead ofone: one complementary to the (+) strand of the target and anothercomplementary to the (−) strand of the target, the polymerase is athermostable polymerase and the reaction temperature is cycled between adenaturation temperature and an extension temperature, therebyexponentially synthesizing a labeled complement to the target sequenceby PCR, (see, e.g., PCR Protocols, 1990, Innis et al. Eds., AcademicPress).

Labeled polynucleotides or polynucleotide analogs may also be chemicallysynthesized using the phosphoramidite or other solution or solid-phasemethods. Detailed descriptions of the chemistry used to formpolynucleotides by the phosphoramidite method are provided elsewhere(see, e.g., Caruthers et al., U.S. Pat. Nos. 4,458,066 and 4,415,732;Caruthers et al., 1982, Genetic Engineering 4:1-17; Users Manual Model392 and 394 Polynucleotide Synthesizers, 1990, pages 6-1 through 6-22,Applied Biosystems, Part No. 901237).

The phosphoramidite method of polynucleotide synthesis is the preferredmethod because of its efficient and rapid coupling on solid support. Thesynthesis is performed with the growing polynucleotide chain attached toa solid support, such that excess reagents, which are in the liquidphase, can be easily removed by decanting, filtration, etc., therebyeliminating the need for purification steps between synthesis cycles.

The following briefly describes the steps of a typical polynucleotidesynthesis cycle using the phosphoramidite method. First, a solid supportincluding a protected nucleoside monomer is treated with acid, e.g.,trichloroacetic acid, to remove the 5′-hydroxyl protecting group,freeing the hydroxyl for a subsequent coupling reaction. An activatedintermediate is then formed by simultaneously adding a protectednucleoside phosphoramidite monomer and a weak acid, e.g., tetrazole, tothe reaction. The weak acid protonates the nitrogen of thephosphoramidite forming a reactive intermediate. Nucleoside addition iscomplete within 30 s. Next, a capping step is performed which terminatesany polynucleotide chains that did not undergo nucleoside addition.Capping is preferably done with acetic anhydride and 1-methylimidazole.The internucleotide linkage is then converted from the phosphite to themore stable phosphotriester by oxidation using iodine as the preferredoxidizing agent and water as the oxygen donor. After oxidation, thehydroxylprotecting group is removed with a protic acid, e.g.,trichloroacetic acid or dichloroacetic acid, and the cycle is repeateduntil chain elongation is complete. After synthesis, the polynucleotidechain is cleaved from the support using a base, e.g., ammonium hydroxideor t-butyl amine. The cleavage reaction also removes any phosphateprotecting groups, e.g., cyanoethyl. Finally, the protecting groups onthe exocyclic amines of the bases and any protecting groups on the dyesare removed by treating the polynucleotide solution in base at anelevated temperature, e.g., 55° C. Preferably the various protectinggroups removed using the mildly basic conditions previously described.

Any of the nucleoside phosphoramidite monomers may be dye-labeledphosphoramidites as described above. If the 5′-terminal position of thenucleotide is labeled, a labeled non-nucleotidic phosphoramidite of theinvention may be used during the final condensation step. If the3′-terminal position or one or more internal position of theoligonucleotide are labeled, a labeled nucleosidic phosphoramidite ofthe invention may be used during any of the condensation steps or,alternatively, using the non-nucleosidic phosphoramidites of theinvention.

Subsequent to synthesis, the polynucleotide may be labeled at a numberof positions, including the 5′-terminus, (see, e.g., Oligonucleotidesand Analogs, Eckstein 1990, Ed., Chapter 8, IRL Press; Orgel et al.,1983, Nucleic Acids Research 11(18):6513; U.S. Pat. No. 5,118,800), thephosphodiester backbone, (see, e.g., Orgel et al., supra, at Chapter 9)or the 3′-terminus (see e.g., Nelson, 1992, Nucleic Acids Research20(23):6253-6259; U.S. Pat. No. 5,401,837 U.S. Pat. No. 5,141,813.) Fora through review of oligonucleotide labeling procedures see R. Hauglandin Excited States of Biopolymers, Steiner Ed., Plenum Press, NY (1983).

In one preferred post-synthesis chemical labeling method anoligonucleotide is labeled as follows. A dye including a carboxy linkinggroup is converted to the N-hydroxysuccinimide ester by reacting withapproximately 1 equivalent of 1,3dicyclohexylcarbodiimide andapproximately 3 equivalents of N-hydroxysuccinimide in dry ethyl acetatefor 3 hours at room temperature. The reaction mixture is washed with 5%HCl, dried over magnesium sulfate, filtered, and concentrated to a solidwhich is resuspended in DMSO. The DMSO dye stock is then added in excess(10-20×) to an aminohexyl derivatized oligonucleotide in 0.25 Mbicarbonate/carbonate buffer at pH 9.4 and allowed to react for 6 hours,e.g., U.S. Pat. No. 4,757,141. The dye labeled oligonucleotide isseparated from unreacted dye by passage through a size-exclusionchromatography column eluting with buffer, e.g., 0.1 molar triethylamineacetate (TEAA). The fraction containing the crude labeledoligonucleotide is further purified by reverse phase HPLC employinggradient elution.

5.6 Kits

In a final aspect, the invention comprises kits comprising themobility-modifying cyanine dyes and/or labeled conjugate of theinvention. In one embodiment, the kits are useful for conjugating themobility-modifying dyes of the invention to other molecules orsubstances. Such kits generally comprise a mobility-modifed dye of theinvention including an optional linking moiety and buffers, solvents,etc. suitable for conjugating the dye to another molecule or substance.

In another embodiment, the kits are useful for labeling enzymaticallysynthesized polynucleotides with the mobility-modifying dyes of theinvention. Such kits generally comprise a labeledenzymatically-incorporable nucleoside/tide or nucleoside/tide analogaccording to the invention, a mixture of enzymatically-incorporablenucleoside/tides or nucleoside/tide analogs capable of supportingcontinuous primer extension and a polymerizing enzyme. Preferably, thelabeled enzymatically-incorporable nucleoside/tide or nucleoside/tideanalog is a compound according to structural formula (II or II.A), mostpreferably a labeled terminator. Preferred polymerizing enzymes arethermostable polymerases such as AMPLITAQ® DNA polymerase FA (PEBiosystems, Foster City, Calif.).

In a final embodiment, the kits are useful for labeling syntheticpolynucleotides with the mobility-modifying dyes of the invention. Suchkits generally comprise a labeled phosphoramidite reagent according tothe invention and synthesis reagents and/or solid supports optionallyfor carrying out oligonucleotide synthesis.

5.7 Methods Utilizing the Dyes and Reagents of the Invention

The mobility-modifying dyes of the invention and conjugatesincorporating the dyes are well suited to any method utilizingfluorescent detection, particularly aqueous applications and methodsrequiring the simultaneous detection of multiple spatially-overlappinganalytes. The various dyes and conjugates of the invention areparticularly well suited for identifying classes of polynucleotides thathave been subjected to a biochemical separation procedure, such aselectrophoresis, or that have been distributed among locations in aspatially-addressable hybridization array.

In a preferred category of methods referred to herein as “fragmentanalysis” or “genetic analysis” methods, labeled polynucleotidefragments are generated through template-directed enzymatic synthesisusing labeled primers or nucleotides, e.g., by ligation orpolymerase-directed primer extension; the fragments are subjected to asize-dependent separation process, e.g., electrophoresis orchromatography; and, the separated fragments are detected subsequent tothe separation, e.g., by laser-induced fluorescence. In a particularlypreferred embodiment, multiple classes of polynucleotides are separatedsimultaneously and the different classes are distinguished by spectrallyresolvable labels.

One such fragment analysis method known as amplified fragment lengthpolymorphism detection (AmpFLP) is based on amplified fragment lengthpolymorphisms, i.e., restriction fragment length polymorphisms that areamplified by PCR. These amplified fragments of varying size serve aslinked markers for following mutant genes through families. The closerthe amplified fragment is to the mutant gene on the chromosome, thehigher the linkage correlation. Because genes for many genetic disordershave not been identified, these linkage markers serve to help evaluatedisease risk or paternity. In the AmpFLPs technique, the polynucleotidesmay be labeled by using a labeled polynucleotide PCR primer, or byutilizing labeled nucleotide triphosphates in the PCR.

In another such fragment analysis method known as nick translation, areaction is used to replace unlabeled nucleotides in a double-stranded(ds) DNA molecule with labeled nucleotides. Free 3′-hydroxyl groups arecreated within the dsDNA by “nicks” caused by treatment withdeoxyribonuclease I (DNAase I). DNA polymerase I then catalyzes theaddition of a labeled nucleotide to the 3′-hydroxyl terminus of thenick. At the same time, the 5′ to 3′-exonuclease activity of this enzymeeliminates the nucleotide at the 5′-phosphoryl terminus of the nick. Anew nucleotide with a free 3′-OH group is incorporated at the positionof the original excised nucleotide, and the nick is shifted along by onenucleotide in the 3′ direction. This 3′ shift will result in thesequential addition of new labeled nucleotides into the dsDNA. Thenick-translated polynucleotide is then analyzed, for example, by using aseparation process such as electrophoresis.

Another exemplary fragment analysis method is based on variable numbersof tandem repeats, or VNTRs. VNTRs are regions of double-stranded DNAthat contain multiple adjacent copies of a particular sequence, with thenumber of repeating units being variable. Examples of VNTR loci arepYNZ22, pMCT118, and Apo B. A subset of VNTR methods are those methodsbased on the detection of microsatellite repeats, or short tandemrepeats (STRs), i.e., tandem repeats of DNA characterized by a short(2-4 bases) repeated sequence. One of the most abundant interspersedrepetitive DNA families in humans is the (dC-dA)_(n)-dG-dT)_(n)dinucleotide repeat family (also called the (CA)_(n) dinucleotide repeatfamily). There are thought to be as many as 50,000 to 100,000 (CA)_(n)repeat regions in the human genome, typically with 15-30 repeats perblock. Many of these repeat regions are polymorphic in length and cantherefore serve as useful genetic markers. Preferably, in VNTR or STRmethods, label is introduced into the polynucleotide fragments using alabeled PCR primer.

In a particularly preferred fragment analysis method, classes identifiedin accordance with the invention are defined in terms of terminalnucleotides so that a correspondence is established between the fourpossible terminal bases and the members of a set of spectrallyresolvable dyes. Such sets are readily assembled from the dyes andenergy-transfer dye pairs of the invention by measuring emission andabsorption bandwidths with commercially available spectrophotometers.More preferably, the classes arise in the context of the chemical orchain termination methods of DNA sequencing, and most preferably theclasses arise in the context of the chain termination methods, i.e.,dideoxy DNA sequencing, or Sanger-type sequencing.

Sanger-type sequencing involves the synthesis of a DNA strand by a DNApolymerase in vitro using a single-stranded or double-stranded DNAtemplate whose sequence is to be determined. Synthesis is initiated at adefined site based on where an oligonucleotide primer anneals to thetemplate. The synthesis reaction is terminated by incorporation of aterminator that will not support continued DNA elongation. When properproportions of dNTPs and a single terminator complementary to A, G, C orT are used, enzyme-catalyzed primer extension will be terminated in afraction of the extension products at each site where the terminator isincorporated. If labeled primers or labeled terminators are used foreach reaction, the sequence information can be detected by fluorescenceafter separation of the resultant primer extension products byhigh-resolution electrophoresis. In the chain termination method, dyesof the invention can be attached to either the sequencing primers orterminators. The dyes can be linked to a complementary functionality onthe 5′-end of the primer, e.g. following the teaching in Fung et al,U.S. Pat. No. 4,757,141; on the base of a primer; or on the base of aterminator, e.g. via the alkynylamino or other linking groups describedabove. Concentration ranges for the various enzymes, primers, dNTPs andlabeled terminators are those commonly employed in the art.

In each of the above fragment analysis methods, labeled extensionproducts are preferably separated by electrophoretic procedures, e.g.Gel Electrophoresis of Nucleic Acids: A Practical Approach, 1981,Rickwood and Hames, Eds., IRL Press Limited, London; Osterman, 1984,Methods of protein and Nucleic Acid Research, Vol. 1 Springer-Verlag,Berlin; or U.S. Pat. Nos. 5,374,527, 5,624,800 and/or 5,552,028.Preferably, the type of electrophoretic matrix is crosslinked oruncrosslinked polyacrylamide having a concentration (weight to volume)of between about 2-20 weight percent. More preferably, thepolyacrylamide concentration is between about 4-8 percent. Preferably,in the context of DNA sequencing, the electrophoresis matrix includes adenaturing agent, e.g., urea, formamide, and the like. Detailedprocedures for constructing such matrices are given by Maniatis et al.,1980, “Fractionation of Low Molecular Weight DNA and RNA inPolyacrylamide Gels Containing 98% Formamide or 7 M Urea,” Methods inEnzymology 65:299-305; Maniatis et al., 1975, “Chain LengthDetermination of Small Double- and Single-Stranded DNA Molecules byPolyacrylamide Gel Electrophoresis,” Biochemistry 14:3787-3794; Maniatiset al., 1982, Molecular Cloning: A Laboratory Manual, Cold Spring HarborLaboratory, New York, pgs. 179-185; and ABI PRISM™ 377 DNA SequencerUser's Manual, Rev. A, January 1995, Chapter 2 (p/n 903433, ThePerkin-Elmer Corporation, Foster City, Calif.). The optimalelectrophoresis conditions, e.g., polymer concentration, pH,temperature, and concentration of denaturing agent, employed in aparticular separation depend on many factors, including among others,the size range of the nucleic acids to be separated, their basecompositions, whether they are single stranded or double stranded, andthe nature of the classes for which information is sought byelectrophoresis. Accordingly, application of the invention may requirestandard preliminary testing to optimize conditions for particularseparations.

Subsequent to electrophoretic separation, the labeled extension productsare detected by measuring the fluorescence emission from the labels. Toperform such detection, the labeled products are illuminated by standardmeans, e.g. high intensity mercury vapor lamps, lasers, or the like. Theillumination wavelength will depend upon the spectral properties of theparticular label. Preferably, the illumination means is a laser havingan illumination beam at a wavelength greater than 620 nm. As themobility-modifying dyes of the invention generally absorb and emit lightin the red region of the visible spectrum, more preferably, theillumination means is a 633 solid state HeNe laser at 638 nm. Severalargon ion lasers are available commercially which lase simultaneously atthese lines, e.g. Cyonics, Ltd. (Sunnyvale, Calif.) Model 2001, or thelike. The fluorescence is then detected by a light-sensitive detector,e.g., a photomultiplier tube, a charged coupled device, or the like.Suitable exemplary electrophoresis detection systems are describedelsewhere, e.g., U.S. Pat. Nos. 5,543,026; 5,274,240; 4,879,012;5,091,652 and 4,811,218.

In preferred embodiments, the primer is unlabeled and the sequencingreaction includes, in addition to the polymerase and mixture of dNTPs, amixture of four different terminators, one complementary to A, onecomplementary to G, one complementary to C and one complementary to T.Each of the different terminators is labeled with a different,spectrally resolvable dye. One of the terminators is labeled with a dyeof the invention. As each of the labeled terminators fluoresces at adifferent wavelength, following separation based on size, the identityof the 3′-terminal nucleotide of each extension product is identified bythe wavelength (or color) of the label. In particularly preferredembodiments, each of the different spectrally resolvable labels can beexcited using a single light source. A set of such preferred labeledterminators is provided in the Examples section. Other sets will dependupon the excitation and emission spectral properties of the variouslabels, the described mobility shift, etc., and are readily obtained asdescribed herein.

The invention having been described, the following examples are providedto illustrate, and not limit, the invention.

1. EXAMPLE Compound Syntheses

This Example provides synthetic methods for certain exemplary compoundsaccording to the invention.

1.1 Synthesis of 4-(Hydroxymethyl)-1,3-Benzenedisulfonic Acid, DisodiumSalt (Compound 42)

4-Formyl-1,3-benzenedisulfonic acid, disodium salt hydrate (41 fromAldrich Chemical Co.) (15 g) was dissolved in methanol (300 ml),followed by the slow addition of sodium borohydride (1.5 g). Thesolution was allowed to stir overnight. A white precipitate was filteredoff, and the supernate was evaporated to dryness under vacuum yielding41 as a white solid (15.5 g). NMR (D₂O) showed a singlet at 4.95 ppmcorresponding to the benzylic methylene protons, and the absence of asinglet at 10.6 ppm corresponding to the aldehyde proton.

1.2 Synthesis of 4-(Bromomethyl)-1,3-Benzenedisulfonic Acid, DisodiumSalt (Compound 43)

4-(hydroxymethyl)-1,3-benzenedisulfonic acid, disodium salt (42 fromabove) (8 g) and lithium bromide (3 g) were dissolved in 48% hydrobromicacid (95 g) and heated at 80° C. for 12 hr. The insoluble material wasfiltered, and the supernate was evaporated to dryness under vacuum. Theresulting white solid was refluxed in 300 ml of acetone, and theinsoluble material was filtered off. The acetone soluble fraction wasevaporated to dryness under vacuum yielding a mixture of 42 and 43 as atan solid (3.2 g). NMR (D₂O) showed a singlet at 4.95 ppm correspondingto the benzylic hydroxymethyl methylene protons from 42, and a singletat 4.90 ppm corresponding to the benzylic bromomethyl methylene protonsfrom 43. Integration of the proton signals showed the ratio ofhydroxymethyl methylene protons from 42 to bromomethyl methylene protonsfrom 43 to be 1:2.

1.3 Synthesis of N-Benzyl Alkylated 2,3,3-Trimethylbenz(e)indolenine(Compound 58)

2,3,3-Trimethylbenz(e)indolenine 57 (Aldrich Chemical) (1 gram, 0.004785moles) was mixed with 2 equivalents of 2,4-disulfo-benzyl bromide 43(3.2 grams, 0.00957 mole) in 3 mL of anhydrous nitrobenzene. Afterheating with stirring at 190° C. for 30 min under an Argon atmosphere,the reaction was cooled and ether added to precipitate crude1-(2,4-disulfo-benzyl)-2,3,3-trimethylbenz(e)indolenine intermediate 58.Crude Compound 58 was recrystallized by suspension in methanol andprecipitation by diethyl ether. Pure Compound 58 was then isolated byfiltration and dried in a vacuum oven to give a tan solid (1 gram, yield39%).

1.4 Synthesis of N-Hexanoate Alkylated 2,3,3-Trimethylbenz(e)indolenine(Compound 59)

2,3,3-trimethylbenz(e)indolenine 57 (4 grams, 0.0159 moles) was mixedwith 1 equivalent of 6-bromohexanoic acid 43 (3.1 grams, 0.0159 mole) in8 mL of anhydrous nitrobenzene. The reaction was heated (120° C.) andstirred for 16 hrs under an argon atmosphere, the reaction was cooledand ether added to precipitate crude1-(6-carboxyhexyl)-2,3,3-trimethylbenz(e)indolenine 59. Crude Compound59 was recrystallized by suspension in ethanol and precipitation bydiethyl ether. Pure Compound 59 was then isolated by filtration anddried in a vacuum oven to give 5.02 grams as an off white solid (yield71%).

1.5 Synthesis of Cyanine Dye Intermediate Compound 20

N-Hexyl-6-carboxylate modified indolenine intermediate 59 (1.2 gm,0.00341 mole) was mixed with 1.2 equivalent of malonaldehydebis(phenylimine) monohydrochloride (Aldrich Chemical) (1.05 gm, 0.0041mole) in 15 mL of acetic anhydride After reflux for 1.5 hr, the reactionwas cooled and diethyl ether added to precipitate the intermediate 20 inquantitative yield as a tan solid.

1.6 Synthesis of Mobility-Modifying Cyanine Dye MM-Cy5 (Compound 21)

Intermediate 20 (100 mg, 0.000174 mole) was mixed with one equivalent of1-(2,4-disulfo-benzyl)-2,3,3-trimethylbenz(e)indolenine intermediate 58(94 mg, 0.000174 mole), 2 equivalents of dry triethylamine (49 uL), and5 ml of dry ethanol. After stirring at reflux for 30 min, the reactionmixture was cooled and the crude mobility-modifying dye 21 wasprecipitated with diethyl ether. The dye 21 was purified bychromatography on silica gel eluting with methanol:CH₂Cl₂ (1:4),followed by recrystallization from methanol/diethyl ether to give 57 mgof dye 21 as dark blue powder (40% yield).

1.7 Synthesis of MM-Cy5-NHS Ester (Compound 22)

Mobility-modifying cyanine dye 21 (30 mg, 0.00003674 mole), 2 mL of drydimethyl formamide, 6 equivalents of di-isopropyl ethylamine (40 μl),and 15 equivalents of O-(N-succinimidyl)-N,N,N′,N′-tetramethyluroniumtetrafluoroborate were stirred at room temperature for 15 minutes. Thereaction was quenched with 5% HCl, extracted 3 times with ethyl acetate,and the combined organic layers were washed with brine and concentratedto give crude NHS ester 22 as a blue solid. The NHS ester 22 waspurified by chromatography on silica gel eluting withmethanol/CH₂Cl₂/AcOH (15:85:0.1). The purified NHS ester 22 was thenrecrystallized from methanol/diethyl ether yielding a dark blue powder(27 mg, 80% yield).

1.8 Synthesis of 7-Propargylamino-ddATP (Compound 23)

7-Propargylamino-ddATP 23 was synthesized according to the methodsdescribed in U.S. Pat. No. 5,151,507.

1.9 Synthesis of MM-Cy5-Labeled Terminator 7-Deaza-ddATP (Compound 24)

Compound 23 (10 μl of a 30 mM solution in 100 mM TEA-bicarbonate, pH7.0) was evaporated to dryness. It was then resuspended in 50 μl 250 mMbicarbonate buffer (pH 9.0). A solution of NHS ester 22 (5 μl of a stockof 5 mg/60 μl in dimethyl sulfoxide) was added and stirred in the darkovernight at room temperature. The reaction mixture was purified by HPLC(AX-300 anion exchange). The fractions corresponding to the labeledterminator 24 were concentrated and repurified by HPLC (C-8 reversephase). The final product was dried in vacuo and diluted with 250 mMCAPSO, pH 9.6.

1.10 Synthesis of Additional Dye-Labeled Terminators

The following additional terminators were synthesized using synthesisstrategies similar to those outlined above. The benzorhodamine NHS esterprecursors were synthesized as described in U.S. Pat. No. 5,936,087. Theextended rhodamine NHS ester precursors were synthesized as described inco-pending application Ser. No. 09/325,243, filed Nov. 17, 1998. Thevarious linker-modified ddNTPs were synthesized as described in U.S.Pat. No. 5,821,356 and/or 5,770,716.

2. EXAMPLE Terminators Labeled with Mobility-Modifying Dyes of theInvention Act as Substrates for Polymerizing Enzymes

Terminators 25, 26, 27, 28, 29, 30, 31, 32, 33 and 34 were used togenerate sequencing fragments according to the protocol described inU.S. Pat. No. 5,948,648 (Example 12) or U.S. Pat. No. 5,847,162(Examples 8-10). Mobility-modifying terminators 29 and 32 retained highbiological activity, as evidenced by their efficient incorporation intothe terminated fragments.

3. EXAMPLE The Mobility-Modifying Dyes of the Invention Shift theRelative Electrophoretic Mobilities of Polynucleotides

3.1 Experimental Protocol

The sequencing fragments generated from the sequencing reactions in theprevious example were applied to a ABI PRIZM® 310 Genetic Analyzer (PEBiosystems, Foster City, Calif.) modified with a red laser andelectrophoresed according to the manufacturers protocol or the protocolsdescribed in U.S. Pat. No. 5,948,648 or U.S. Pat. No. 5,847,162.

3.2 Results

The electrophoretic mobilities of fragments labeled with the cyaninedyes relative to those labeled with the rhodamine dyes are tabulated inTABLE 1, below. In the table, a positive (+) shift indicates fragmentsmigrated faster than the standards. A negative (−) shift indicatesfragments that migrated slower than the standards. TABLE 1 RelativeMobilities of Dye-Labeled Sequencing Fragments Relative Mobilities (BaseUnits) +0.5 0.0 −0.5 −1.0 −1.5 −2.0 Terminator 26 27 24 25 28 29 30 3132 34 33

As illustrated in TABLE 1, fragments generated from monosulfonatedbenzocyanine dye-labeled terminators 25 (ddA), 30 (ddG) and 34 (ddU)migrate two or more bases slow during electorphoresis relative to DNAfragments generated from dibenzorhodamine dye (U.S. Pat. No. 5,936,087)labeled terminators 26 (ddG), 27 (ddA), 28 (ddG), and 31 (ddC), orextended rhodamine dye (U.S. application Ser. No. 09/325,243; attorneydocket no. 4446) labeled terminator 33 (ddU). Mobility-modifying themonosulfonated dye according the the invention by replacing themonosulfonate group with a bis-sulfonated mobility-modifying moietyincreases the relative electrophoretic mobilties of polynucleotidefragments labeled with the mobility-modifying dye by one base, asdemonstrated by labeled fragments generated with terminators 24 (ddA),29 (ddG) and 32 (ddC).

All publications, patents and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by reference.

The invention now having been fully described, it will be apparent toone of ordinary skill in the art that many changes and modifications canbe made thereto without departing from the spirit or scope of theappended claims.

1. A mobility-modifying cyanine dye comprising: (i) a first substitutedor unsubstituted parent heteroaromatic benzazole/benzazolium ring systemhaving a linking moiety of the formula -L-LG, where L is a linker and LGis a linking group, attached to the heteroaromatic ring nitrogen; (ii) asecond substituted or unsubstituted parent heteroaromaticbenzazole/benzazolium ring system having a mobility-modifying moietyattached to the heteroaromatic ring nitrogen; and an electrondelocalizing bridge connecting the first and second parentbenzazole/benzazolium rings via their respective C2 carbons, whereinwhen said mobility-modifying moiety has a net charge of −2 or less or +1or greater.
 2. The mobility-modifying cyanine dye of claim 1 in whichthe bridge is a compound selected from the group consisting of:—(CR¹═CR²)_(k)(CR³═CR⁴)_(l)—(CR⁵—CR⁶)_(m)—CR⁷═  (B.1)and

wherein: k, l, and m are each independently integers from 0 to 1; R¹,R², R³, R⁴, R⁵, R⁶ and R⁷ are each independently selected from the groupconsisting of hydrogen, halogen, —F, —Cl, —CN, —CF₃, (C₁-C₆) alkyl,(C₅-C₁₄) aryl or 5-14 membered heteroaryl; R¹⁰ and R^(10′) are eachindependently selected from the group consisting of hydrogen, oxygen,halogen, —F, —Cl, —CN, —CF₃, —OR, —SR, —NRR, (C₁-C₆) alkyl, (C₅-C₁₄)aryl or 5-14 membered heteroaryl, where each R is independently hydrogenor (C₁-C₆) alkyl; and p is an integer from 0 to 2, where in structuralformula (B.2), the dotted lines at substituents R^(10′) represent bondsthat may be independently either single bonds or a double bonds,depending upon the identities of the substituents.
 3. Themobility-modifying cyanine dye of claim 2 in which the bridge is acompound of structural formula (B. 1).
 4. The mobility-modifying cyaninedye of claim 3 in which the sum of k, l and m is
 2. 5. Themobility-modifying cyanine dye of claim 2 in which the bridge is acompound of structural formula (B. 1) wherein R¹, R², R³, R⁴, R⁵, R⁶ andR⁷ are each hydrogen.
 6. The mobility-modifying cyanine dye of claim 1in which the bridge is —CH═CH—CH═CH—CH═.
 7. The mobility-modifyingcyanine dye of claim 1 in which the mobility-modifying moiety has a netpositive charge.
 8. The mobility-modifying cyanine dye of claim 1 inwhich the mobility-modifying moiety has a net negative charge.
 9. Themobility-modifying cyanine dye of claim 1 in which themobility-modifying moiety has the structure:

or a salt thereof, wherein: n is an integer from 1 to 6 (preferably 1 to3); R²⁴, when taken alone, is hydrogen, a strong anionic substituent,—S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together with R²⁵ is a benzogroup or a benzo group independently substituted with one or more stronganionic substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups; R²⁵, when takenalone, is hydrogen, a strong anionic substituent, —S(O)₂O⁻, or—O—S(O)₂O⁻, or when taken together with R²⁴ or R²⁶ is a benzo group or abenzo group independently substituted with one or more strong anionicsubstituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups; R²⁶, when taken alone, ishydrogen, a strong anionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or whentaken together with R²⁵ or R²⁷ is a benzo group or a benzo groupindependently substituted with one or more strong anionic substituents,—S(O)₂O⁻, or —O—S(O)₂O⁻ groups; and R²⁷, when taken alone, is hydrogen,a strong anionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when takentogether with R²⁶ or R²⁸ is a benzo group or a benzo group independentlysubstituted with one or more strong anionic substituents, —S(O)₂O⁻, or—O—S(O)₂O⁻ groups; and R²⁸, when taken alone, is hydrogen, a stronganionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken togetherwith R²⁷ is a benzo group or a benzo group independently substitutedwith one or more strong anionic substituents, —S(O)₂O⁻, or OS(O)₂O⁻groups.
 10. The mobility-modifying cyanine dye of claim 1 in which themobility-modifying moiety has the structure:

or a salt thereof, wherein: o is an integer from 1 to 3; q is an integerfrom 1 to 3; R²⁹ is a strong anionic substituent, —S(O)₂O⁻ or—O—S(O)₂O⁻, each R³⁰ is independently selected from the group consistingof hydrogen a strong anionic substituent, —S(O)₂O⁻and —O—S(O)₂O⁻; andR³¹ is selected from the group consisting of hydrogen, a strong anionicsubstitutent, —S(O)₂O⁻, —O—S(O)₂O⁻ and —CH₃, with the proviso that MMhas a net charge of at least −2 at a pH in the range of about pH 6 to pH10.
 11. The mobility-modifying cyanine dye of claim 1 in which the firstand second heteroaromatic benzazole/benzazolium ring systems are thesame.
 12. The mobility-modifying cyanine dye of claim 1 in which thefirst parent heteroaromatic benzazole/benzazolium ring system has thestructure:

or a salt thereof, wherein: Z is selected from the group consisting of—S—, —O—, —Se— and —CR1R⁹—, where R⁸ and R⁹ when taken alone, are eachindependently (C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkylenoor (C₄-C₅) alkano; R¹¹, R¹², R¹³ and R¹⁴, when taken alone, are eachindependently selected from the group consisting of hydrogen, (C₁-C₆)alkyl, (C₁-C₆) alkyl independently substituted with one or more W, 2-6membered heteroalkyl, 2-6 membered heteroalkyl independently substitutedwith one or more W, (C₅-C₁₀) aryl, (C₅-C₁₀) aryl independentlysubstituted with one or more W, (C₅-C₆) arylaryl, (C₅-C₆) arylarylindependently substituted with one or more W, (C₆-C₁₆) arylalkyl,(C₆-C₁₆) independently substituted with one or more W, 6-16 memberedarylheteroalkyl, 6-16 membered arylheteroalkyl independently substitutedwith one or more W, 5-10 membered heteroaryl, 5-10 membered heteroarylindependently substituted with one or more W, 5-6 memberedheteroaryl-heteroaryl, 5-6 membered heteroaryl independently substitutedwith one or more W, 6-16 membered heteroarylalkyl, 6-16 memberedheteroarylalkyl independently substituted with one or more W, 6-16membered heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkylindependently substituted with one or more W, or when taken togetherwith an adjacent R^(n) are each independently selected from the groupconsisting of (C₆-C₁₀) aryleno, (C₆-C₁₀) aryleno independentlysubstituted with one or more W, 6-10 membered heteroaryleno and 6-10membered heteroaryleno independently substituted with one or more W; andeach W is independently —R, —X, ═O, —OR, ═S, —SR, —NRR, ═NR, (C₁-C₆)perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO, —NO₂, =N₂, —N₃, —NHOH,—S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′, —C(O)SR′, —C(S)SR′, and—C(NR)NRR, wherein: each X is independently a halogen; each R isindependently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆) alkyl, (C₁-C₆)alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆)arylalkyl, 5-10 membered heteroaryl or 6-16 membered heteroarylalkyl;and each R′ is independently (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl, 5-10membered heteroaryl or 6-16 membered heteroarylalkyl; and each R″ isindependently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkynyl,(C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10 membered heteroaryl or 6-16membered heteroarylalkyl.
 13. The mobility-modifying cyanine dye ofclaim 1 in which the second parent heteroaromatic benzazole/benzazoliumring system has the structure:

or a salt thereof, wherein: Z′ is selected from the group consisting of—S—, —O—, —Se— and —CR⁸R⁹, where R^(8′) and R^(9′), when taken alone,are each independently (C₁-C₆) alkyl, or when taken together are (C₄-C₅)alkyleno or (C₄-C₅) alkano; R¹⁹, R²⁰, R²¹ and R²², when taken alone, areeach independently selected from the group consisting of hydrogen,(C₁-C₆) alkyl, (C₁-C₆) alkyl independently substituted with one or moreW, 2-6 membered heteroalkyl, 2-6 membered heteroalkyl independentlysubstituted with one or more W, (C₅-C₁₀) aryl, (C₅-C₁₀) arylindependently substituted with one or more W, (C₅-C₆) arylaryl, (C₅-C₆)arylaryl independently substituted with one or more W, (C₆-C₁₆)arylalkyl, (C₆-C₁₆) independently substituted with one or more W, 6-16membered arylheteroalkyl, 6-16 membered arylheteroalkyl independentlysubstituted with one or more W, 5-10 membered heteroaryl, 5-10 memberedheteroaryl independently substituted with one or more W, 5-6 memberedheteroaryl-heteroaryl, 5-6 membered heteroaryl independently substitutedwith one or more W, 6-16 membered heteroarylalkyl, 6-16 memberedheteroarylalkyl independently substituted with one or more W, 6-16membered heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkylindependently substituted with one or more W, or when taken togetherwith an adjacent R^(n) are each independently selected from the groupconsisting of (C₆-C₁₀) aryleno, (C₆-C₁₀) aryleno independentlysubstituted with one or more W, 6-10 membered heteroaryleno and 6-10membered heteroaryleno independently substituted with one or more W; andeach W is independently —R, —X, ═O, —OR, ═S, —SR, —NRR, ═NR, (C₁-C₆)perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO, —NO₂, =N₂, —N₃, —NHOH,—S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′, —C(O)SR′, —C(S)SR′, and—C(NR)NRR, wherein: each X is independently a halogen; each R isindependently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆) alkyl, (C₁-C₆)alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆)arylalkyl, 5-10 membered heteroaryl or 6-16 membered heteroarylalkyl;and each R′ is independently (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arylalkyl, 5-10membered heteroaryl or 6-16 membered heteroarylalkyl; and each R″ isindependently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkynyl,(C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10 membered heteroaryl or 6-16membered heteroarylalkyl.
 14. A mobility-modifying cyanine dye accordingto claim 1 in which the first and second heteroaromaticbenzazole/benzazolium rings are each the same or different substitutedor unsubstituted indoline/indolinium ring.
 15. The mobility-modifyingcyanine dye of claim 1 which has the structure:

or a salt thereof, wherein: k, l, and m are each independently integersfrom 0 to 1; R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are each independentlyselected from the group consisting of hydrogen, halogen, —F, —Cl, —CN,—CF₃, (C₁-C₆) alkyl, (C₅-C₁₄) aryl and 5-14 membered heteroaryl; MM is amobility-modifying moiety; L is a linker; R_(x) is a reactive functionalgroup; Z is selected from the group consisting of —S—, —O—, —Se—and—CR⁸R^(9′), where R⁸ and R⁹ when taken alone, are each independently(C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkyleno or (C₄-C₅)alkano; Z′ is selected from the group consisting of —S—, —O—, —Se— and—CR^(8′)R^(9′), where R^(8′) and R^(9′), when taken alone, are eachindependently (C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkylenoor (C₄-C₅) alkano; R¹¹, R¹², R¹³ and R¹⁴, when taken alone, are eachindependently selected from the group consisting of hydrogen, (C₁-C₆)alkyl, (C₁-C₆) alkyl independently substituted with one or more W, 2-6membered heteroalkyl, 2-6 membered heteroalkyl independently substitutedwith one or more W, (C₅-C₁₀) aryl, (C₅-C₁₀) aryl independentlysubstituted with one or more W, (C₅-C₆) arylaryl, (C₅-C₆) arylarylindependently substituted with one or more W, (C₆-C₁₆) arylalkyl,(C₆-C₁₆) independently substituted with one or more W, 6-16 memberedarylheteroalkyl, 6-16 membered arylheteroalkyl independently substitutedwith one or more W, 5-10 membered heteroaryl, 5-10 membered heteroarylindependently substituted with one or more W, 5-6 memberedheteroaryl-heteroaryl, 5-6 membered heteroaryl independently substitutedwith one or more W, 6-16 membered heteroarylalkyl, 6-16 memberedheteroarylalkyl independently substituted with one or more W, 6-16membered heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkylindependently substituted with one or more W, or when taken togetherwith an adjacent R^(n) are each independently selected from the groupconsisting of (C₆-C₁₀) aryleno, (C₆-C₁₀) aryleno independentlysubstituted with one or more W, 6-10 membered heteroaryleno and 6-10membered heteroaryleno independently substituted with one or more W;R¹⁹, R²⁰, R²¹ and R²², when taken alone, are each independently selectedfrom the group consisting of hydrogen, (C₁-C₆) alkyl, (C₁-C₆) alkylindependently substituted with one or more W, 2-6 membered heteroalkyl,2-6 membered heteroalkyl independently substituted with one or more W,(C₅-C₁₀) aryl, (C₅-C₁₀) aryl independently substituted with one or moreW, (C₅-C₆) arylaryl, (C₅-C₆) arylaryl independently substituted with oneor more W, (C₆-C₁₆) arylalkyl, (C₆-C₁₆) independently substituted withone or more W, 6-16 membered arylheteroalkyl, 6-16 memberedarylheteroalkyl independently substituted with one or more W, 5-10membered heteroaryl, 5-10 membered heteroaryl independently substitutedwith one or more W, 5-6 membered heteroaryl-heteroaryl, 5-6 memberedheteroaryl independently substituted with one or more W, 6-16 memberedheteroarylalkyl, 6-16 membered heteroarylalkyl independently substitutedwith one or more W, 6-16 membered heteroaryl-heteroalkyl and 6-16membered heteroaryl-heteroalkyl independently substituted with one ormore W, or when taken together with an adjacent R^(n) are eachindependently selected from the group consisting of (C₆-C₁₀) aryleno,(C₆-C₁₀) aryleno independently substituted with one or more W, 6-10membered heteroaryleno and 6-10 membered heteroaryleno independentlysubstituted with one or more W; each W is independently —R, —X, ═O, —OR,═S, —SR, —NRR, =NR, (C₁-C₆) perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO,—NO₂, =N₂, —N₃, —NHOH, —S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′,—C(O)SR′, —C(S)SR′, and —C(NR)NRR, wherein: each X is independently ahalogen; each R is independently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆)alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₅-C₁₀) aryl,(C₆-C₁₆) arylalkyl, 5-10 membered heteroaryl or 6-16 memberedheteroarylalkyl; and each R′ is independently (C₁-C₆) alkyl, (C₁-C₆)alkanyl, (C₂-C₆) alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆)arylalkyl, 5-10 membered heteroaryl or 6-16 membered heteroarylalkyl;and each R″ is independently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10 membered heteroaryl or6-16 membered heteroarylalkyl.
 16. The mobility-modifying cyanine dye ofclaim 15 in which Z is —NR⁸R⁹—, where R⁸ and R⁹ are each independently(C₁-C₆) alkano; and Z′ is —NR^(8′)R^(9′), where R^(8′) and R^(9′) areeach independently (C₁-C₆) alkano.
 17. The mobility-modifying cyaninedye of claim 15 which is selected from the group consisting of:

or a salt thereof, wherein: R¹¹, R¹², R¹³, R¹⁴, R¹⁹, R²⁰, R²¹, R²², R³⁰,R³¹, R³², R³³, R³⁴, R³⁵, R³⁶ and R³⁷ are each independently selectedfrom the group consisting of hydrogen, —S(O)₂O⁻ and —O—S(O)₂O⁻.
 18. Alabeled nucleoside/tide or nucleoside/tide analog having the structure:NUC-L′-R⁴¹-L-D or a salt thereof, wherein: D is a mobility-modifyingcyanine dye chromophore; L is a first linker which is attached to D at aheteroaromatic ring nitrogen; R⁴¹ is a covalent linkage; NUC is anucleoside/tide or nucleoside/tide analog; and L′ is a second linkerwhich is attached to the nucleobase or sugar moiety of NUC.
 19. Thelabeled nucleoside/tide or nucleoside/tide analog of claim 18 which isenzymatically incorporable.
 20. The labeled nucleoside/tide ornucleoside/tide analog of claim 18 which is a terminator.
 21. Thelabeled nucleoside/tide or nucleoside/tide analog of claim 18 which isenzymatically extendable.
 22. The labeled nucleoside/tide ornucleoside/tide analog of claim 18 in which -L′-NUC taken together hasthe structure:

or a salt thereof, wherein: B is a nucleobase; L′ is (C₁-C₂₀) alkyldiyl,(C₁-C₂₀) alkyleno, (C₂-C₂₀) alkyno, (C₂-C₂₀) alkeno 2-20 memberedheteroalkyldiyl, 2-20 membered heteroalkyleno, 2-20 memberedheteroalkyno or 2-20 membered heteroalkeno; R⁷⁰ and R⁷¹, when takenalone, are each independently selected from the group consisting ofhydrogen, hydroxyl and a moiety which blocks polymerase-mediatedtemplate-directed polymerization, or when taken together form a bondsuch that the illustrated sugar is 2′,3′-didehydroribose; and R⁷² isselected from the group consisting of hydroxyl, a phosphate ester havingthe formula

where α is an integer from 0 to 2 and a phosphate ester analog.
 23. Thelabeled nucleoside/tide or nucleoside/tide analog of claim 22 in whichL′ is selected from the group consisting of: —C≡C—CH₂—, where theterminal sp carbon is covalently attached to nucleobase B and theterminal methylene (sp³) carbon is covalently attached to R⁴¹; and—C≡C—CH₂—OCH₂—CH₂—NR⁴⁷—R⁴⁸—, where R⁴⁷ is hydrogen or (C₁-C₆) alkyl andR⁴⁸ is —C(O)—(CH₂)_(r)—, —C(O)—CHR⁴⁹—, —C(O)C≡C—CH₂— or—C(O)-φ-CH₂)_(r)—, where each r is independently an integer from 1 to 5and φ is C₆ aryldiyl or 6-membered heteroaryldiyl and R⁴⁹ is hydrogen,(C₁-C₆) alkyl or a side chain of an encoding or non-encoding amino acid,and where the terminal sp carbon is covalently attached to nucleobase Band the other terminal group is covalently attached to R⁴¹.
 24. Thelabeled nucleoside/tide or nucleoside/tide analog of claim 22 in whichnucleobase B is a purine, a 7-deazapurine, a pyrimidine, a normalnucleobase or a common analog of a normal nucleobase.
 25. The labelednucleoside/tide or nucleoside/tide analog of claim 18 in which D has thestructure:

or a salt thereof, wherein: k, l, and m are each independently integersfrom 0 to 1; R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are each independentlyselected from the group consisting of hydrogen, halogen, —F, —Cl, —CN,—CF₃, (C₁-C₆) alkyl, (C₅-C₁₄) aryl or 5-14 membered heteroaryl; MM is amobility-modifying moiety; Z is selected from the group consisting of—S—, —O⁻, —Se— and —CR⁸R⁹—, where R⁸ and R⁹ when taken alone, are eachindependently (C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkylenoor (C₄-C₅) alkano; Z′ is selected from the group consisting of —S—, —O—,—Se— and —CR^(8′)R^(9′), where R^(8′) and R^(9′), when taken alone, areeach independently (C₁-C₆) alkyl, or when taken together are (C₄-C₅)alkyleno or (C₄-C₅) alkano; R¹¹, R¹², R¹³ and R¹⁴, when taken alone, areeach independently selected from the group consisting of hydrogen,(C₁-C₆) alkyl, (C₁-C₆) alkyl independently substituted with one or moreW, 2-6 membered heteroalkyl, 2-6 membered heteroalkyl independentlysubstituted with one or more W, (C₅-C₁₀) aryl, (C₅-C₁₀) arylindependently substituted with one or more W, (C₅-C₆) arylaryl, (C₅-C₆)arylaryl independently substituted with one or more W, (C₆-C₁₆)arylalkyl, (C₆-C₁₆) independently substituted with one or more W, 6-16membered arylheteroalkyl, 6-16 membered arylheteroalkyl independentlysubstituted with one or more W, 5-10 membered heteroaryl, 5-10 memberedheteroaryl independently substituted with one or more W, 5-6 memberedheteroaryl-heteroaryl, 5-6 membered heteroaryl independently substitutedwith one or more W, 6-16 membered heteroarylalkyl, 6-16 memberedheteroarylalkyl independently substituted with one or more W, 6-16membered heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkylindependently substituted with one or more W, or when taken togetherwith an adjacent R^(n) are each independently selected from the groupconsisting of (C₆-C₁₀) aryleno, (C₆-C₁₀) aryleno independentlysubstituted with one or more W, 6-10 membered heteroaryleno and 6-10membered heteroaryleno independently substituted with one or more W;R¹⁹, R²⁰, R²¹ and R²², when taken alone, are each independently selectedfrom the group consisting of hydrogen, (C₁-C₆) alkyl, (C₁-C₆) alkylindependently substituted with one or more W, 2-6 membered heteroalkyl,2-6 membered heteroalkyl independently substituted with one or more W,(C₅-C₁₀) aryl, (C₅-C₁₀) aryl independently substituted with one or moreW, (C₅-C₆) arylaryl, (C₅-C₆) arylaryl independently substituted with oneor more W, (C₆-C₁₆) arylalkyl, (C₆-C₁₆) independently substituted withone or more W, 6-16 membered arylheteroalkyl, 6-16 memberedarylheteroalkyl independently substituted with one or more W, 5-10membered heteroaryl, 5-10 membered heteroaryl independently substitutedwith one or more W, 5-6 membered heteroaryl-heteroaryl, 5-6 memberedheteroaryl independently substituted with one or more W, 6-16 memberedheteroarylalkyl, 6-16 membered heteroarylalkyl independently substitutedwith one or more W, 6-16 membered heteroaryl-heteroalkyl and 6-16membered heteroaryl-heteroalkyl independently substituted with one ormore W, or when taken together with an adjacent R^(n) are eachindependently selected from the group consisting of (C₆-C₁₀) aryleno,(C₆-C₁₀) aryleno independently substituted with one or more W, 6-10membered heteroaryleno and 6-10 membered heteroaryleno independentlysubstituted with one or more W; each W is independently —R, —X, ═O, —OR,═S, —SR, —NRR, ═NR, (C₁-C₆) perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO,—NO₂, =N₂, —N₃, —NHOH, —S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′,—C(O)SR′, —C(S)SR′, and —C(NR)NRR, wherein: each X is independently ahalogen; each R is independently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆)alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₅-C₁₀) aryl,(C₆-C₁₆) arylalkyl, 5-10 membered heteroaryl or 6-16 memberedheteroarylalkyl; each R′ is independently (C₁-C₆) alkyl, (C₁-C₆)alkanyl, (C₂-C₆) alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆)arylalkyl, 5-10 membered heteroaryl or 6-16 membered heteroarylalkyl;and each R″ is independently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10 membered heteroaryl or6-16 membered heteroarylalkyl; and the dotted line at the heteroaromaticring nitrogen indicates the point of attachment of linker L.
 26. Amobility-modifying phosphoramidite reagent having the structure:

or a salt thereof, wherein: N, O and P are nitrogen, oxygen andphosphorous, respectively; D is a mobility-modifying dye chromophore ora protected derivative thereof; L is a first linker; R⁴¹ is a bond or acovalent linkage; L″ is a bond or a second linker; R⁶⁰ is a phosphiteester protecting group; R⁶¹, when taken alone, is selected from thegroup consisting of (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl,(C₂-C₆) alkynyl, (C₃-C₁₀) cycloalkyl, (C₅-C₂₀) aryl and (C₆-C₂₆)arylalkyl, or when taken together with R⁶² forms a straight-chain orbranched (C₂-C₁₀) alkyleno or a straight-chain or branched 2-10 memberedheteroalkyleno; and R⁶², when taken alone, is selected from the groupconsisting of (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆)alkynyl, (C₃-C₁₀) cycloalkyl, (C₅-C₂₀) aryl and (C₆-C₂₆) arylalkyl, orwhen taken together with R⁶² forms a straight-chain or branched (C₂-C₁₀)alkyleno or a straight-chain or branched 2-10 membered heteroalkyleno.27. The mobility-modifying phosphoramidite reagent according to claim 26which has the structure:

wherein: N, P and O are nitrogen, phosphorous and oxygen, respectively;R⁴¹, L, D, R⁶⁰, R⁶¹ and R⁶² are as previously defined; R⁶³ is hydrogenor an acid-labile hydroxylprotecting group; and v is an integer from 1to
 30. 28. A mobility-modifying phosphoramidite reagent having thestructure:

or a salt thereof, wherein: O, P and N are oxygen, phosphorous andnitrogen, respectively; B is a nucleobase or a protected derivativethereof; D is a mobility-modifying dye chromophore or a protectedderivative thereof; L is a first linker which is attached to D at aheteroaromatic ring nitrogen; R⁴¹ is a bond or a covalent linkage; L′ isa bond or a second linker; R⁶⁰ is a phosphite ester protecting group;R⁶¹, when taken alone, is selected from the group consisting of (C₁-C₆)alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₃-C₁₀)cycloalkyl, (C₅-C₂₀) aryl and (C₆-C₂₆) arylalkyl, or when taken togetherwith R⁶² forms a straight-chain or branched (C₂-C₁₀) alkyleno or astraight-chain or branched 2-10 membered heteroalkyleno; and R⁶², whentaken alone, is selected from the group consisting of (C₆-C₆) alkyl,(C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₃-C₁₀) cycloalkyl,(C₅-C₂₀) aryl and (C₆-C₂₆) arylalkyl, or when taken together with R⁶¹forms a straight-chain or branched (C₂-C₁₀) alkyleno or a straight-chainor branched 2-10 membered heteroalkyleno; and R⁶³ is hydrogen or anacid-labile hydroxyl protecting group
 29. The mobility-modifyingphosphoramidite reagent according to claim 26, 27 or 28 in which D hasthe structure:

or a salt thereof, wherein: k, l, and m are each independently integersfrom 0 to 1; R¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are each independentlyselected from the group consisting of hydrogen, halogen, —F, —Cl, —CN,—CF₃, (C₁-C₆) alkyl, (C₅-C₁₄) aryl or 5-14 membered heteroaryl; MM is amobility-modifying moiety; Z is selected from the group consisting of—S—, —O—, —Se— and —CR⁸R⁹—, where R⁸ and R⁹ when taken alone, are eachindependently (C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkylenoor (C₄-C₅) alkano; Z′ is selected from the group consisting of —S—, —O—,—Se— and —CR^(8′)R^(9′), where R⁸ and R⁹ when taken alone, are eachindependently (C₁-C₆) alkyl, or when taken together are (C₄-C₅) alkylenoor (C₄-C₅) alkano; R¹¹, R¹², R¹³ and R¹⁴, when taken alone, are eachindependently selected from the group consisting of hydrogen, (C₁-C₆)alkyl, (C₁-C₆) alkyl independently substituted with one or more W, 2-6membered heteroalkyl, 2-6 membered heteroalkyl independently substitutedwith one or more W, (C₅-C₁₀) aryl, (C₅-C₁₀) aryl independentlysubstituted with one or more W, (C₅-C₆) arylaryl, (C₅-C₆) arylarylindependently substituted with one or more W, (C₆-C₁₆) arylalkyl,(C₆-C₁₆) independently substituted with one or more W, 6-16 memberedarylheteroalkyl, 6-16 membered arylheteroalkyl independently substitutedwith one or more W, 5-10 membered heteroaryl, 5-10 membered heteroarylindependently substituted with one or more W, 5-6 memberedheteroaryl-heteroaryl, 5-6 membered heteroaryl independently substitutedwith one or more W, 6-16 membered heteroarylalkyl, 6-16 memberedheteroarylalkyl independently substituted with one or more W, 6-16membered heteroaryl-heteroalkyl and 6-16 membered heteroaryl-heteroalkylindependently substituted with one or more W, or when taken togetherwith an adjacent R^(n) are each independently selected from the groupconsisting of (C₆-C₁₀) aryleno, (C₆-C₁₀) aryleno independentlysubstituted with one or more W, 6-10 membered heteroaryleno and 6-10membered heteroaryleno independently substituted with one or more W;R¹⁹, R²⁰, R²¹ and R²², when taken alone, are each independently selectedfrom the group consisting of hydrogen, (C₁-C₆) alkyl, (C₁-C₆) alkylindependently substituted with one or more W, 2-6 membered heteroalkyl,2-6 membered heteroalkyl independently substituted with one or more W,(C₅-C₁₀) aryl, (C₅-C₁₀) aryl independently substituted with one or moreW, (C₅-C₆) arylaryl, (C₅-C₆) arylaryl independently substituted with oneor more W, (C₆-C₁₆) arylalkyl, (C₆-C₁₆) independently substituted withone or more W, 6-16 membered arylheteroalkyl, 6-16 memberedarylheteroalkyl independently substituted with one or more W, 5-10membered heteroaryl, 5-10 membered heteroaryl independently substitutedwith one or more W, 5-6 membered heteroaryl-heteroaryl, 5-6 memberedheteroaryl independently substituted with one or more W, 6-16 memberedheteroarylalkyl, 6-16 membered heteroarylalkyl independently substitutedwith one or more W, 6-16 membered heteroaryl-heteroalkyl and 6-16membered heteroaryl-heteroalkyl independently substituted with one ormore W, or when taken together with an adjacent R^(n) are eachindependently selected from the group consisting of (C₆-C₁₀) aryleno,(C₆-C₁₀) aryleno independently substituted with one or more W, 6-10membered heteroaryleno and 6-10 membered heteroaryleno independentlysubstituted with one or more W; each W is independently —R, —X, ═O, —OR,═S, —SR, —NRR, ═NR, (C₁-C₆) perhaloalkyl, —CX₃, —CN, —OCN, —SCN, —NO,—NO₂, =N₂, —N₃, —NHOH, —S(O)₂R, —C(O)R, —C(S)R, —C(O)OR′, —C(S)OR′,—C(O)SR′, —C(S)SR′, and —C(NR)NRR, wherein: each X is independently ahalogen; each R is independently —H, —NR″R″, —C(O)R″, —S(O₂)R″, (C₁-C₆)alkyl, (C₁-C₆) alkanyl, (C₂-C₆) alkenyl, (C₂-C₆) alkynyl, (C₅-C₁₀) aryl,(C₆-C₁₆) arylalkyl, 5-10 membered heteroaryl or 6-16 memberedheteroarylalkyl; each R′ is independently (C₁-C₆) alkyl, (C₁-C₆)alkanyl, (C₂-C₆) alkenyl and (C₂-C₆) alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆)arylalkyl, 5-10 membered heteroaryl or 6-16 membered heteroarylalkyl;and each R″ is independently —H, (C₁-C₆) alkyl, (C₁-C₆) alkanyl, (C₂-C₆)alkynyl, (C₅-C₁₀) aryl, (C₆-C₁₆) arlyalkyl, 5-10 membered heteroaryl or6-16 membered heteroarylalkyl; and the dotted line at the heteroaromaticring nitrogen indicates the point of attachment of linker L.
 30. Themobility-modifying phosphoramidite reagent of claim 29 in which MM hasthe structure:

or a salt thereof, wherein: n is an integer from 1 to 6 (preferably 1 to3); R²⁴, when taken alone, is hydrogen, a strong anionic substituent,—S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken together with R²⁵ is a benzogroup or a benzo group independently substituted with one or more stronganionic substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups; R²⁵, when takenalone, is hydrogen, a strong anionic substituent, —S(O)₂O⁻, or—O—S(O)₂O⁻, or when taken together with R²⁴ or R²⁶ is a benzo group or abenzo group independently substituted with one or more strong anionicsubstituents, —S(O)₂O⁻, or —O—S(O)₂O⁻ groups; R²⁶, when taken alone, ishydrogen, a strong anionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or whentaken together with R²⁵ or R²⁷ is a benzo group or a benzo groupindependently substituted with one or more strong anionic substituents,—S(O)₂O⁻, or —O—S(O)₂O⁻ groups; and R²⁷, when taken alone, is hydrogen,a strong anionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when takentogether with R²⁶ or R²⁸ is a benzo group or a benzo group independentlysubstituted with one or more strong anionic substituents, —S(O)₂O⁻, or—O—S(O)₂O⁻ groups; and R²⁸, when taken alone, is hydrogen, a stronganionic substituent, —S(O)₂O⁻, or —O—S(O)₂O⁻, or when taken togetherwith R²⁷ is a benzo group or a benzo group independently substitutedwith one or more strong anionic substituents, —S(O)₂O⁻, or —O—S(O)₂O⁻groups.
 31. The mobility-modifying phosphoramidite reagent according toclaim 26, 27 or 28 in which L is —CH₂—CH₂—CH₂—CH₂—CH₂— (pentano). 32.The mobility-modifying phosphoramidite reagent according to claim 26, 27or 28 in which R⁴¹ is a covalent linkage formed upon the reactionbetween an electrophile and a nucleophile.
 33. The mobility-modifyingphosphoramidite reagent according to claim 31 in which R⁴¹ has thestructure —(O)NR⁵⁶—, where R⁵⁶ is hydrogen or (C₁-C₆) alkyl.
 34. Apolynucleotide labeled with a mobility-modifying dye according toclaim
 1. 35. A method of generating a labeled primer extension product,comprising the step of enzymatically extending a primer-target hybrid inthe presence of a mixture of enzymatically-extendable nucleotidescapable of supporting continuous primer extension and a terminator,wherein said primer or said terminator is labeled with amobility-modifying dye according to claim
 1. 36. The method of claim 35in which the terminator is a mixture of four different terminators, onewhich terminates at a template A, one which terminates at a template G,one which terminates at a template C and one which terminates at atemplate T or U and wherein at least one of the terminators is labeledwith a mobility-modifying dye according to claim
 1. 37. The method ofclaim 36 in which each of the four different terminators is labeled witha different, spectrally-resolvable fluorophore, and one of theterminators is selected from the group consisting of Compound 29 andCompound
 32. 38. A kit for generating a labeled primer extensionproduct, comprising enzymatically-extendable nucleotides capable ofsupporting continuous primer extension and a terminator, wherein saidprimer or said terminator is labeled with a mobility-modifying cyaninedye according to claim
 1. 39. The kit of claim 38 in which theterminator is a set of four different mobility-modified terminators, onewhich terminates at a template A, one which terminates at a template G,one which terminates at a template C and one which terminates at atemplate T or U.
 40. The kit of claim 39 in which the set of fourdifferent terminators is a set of mobility-matched terminators.
 41. Thekit of claim 39 in which the set of mobility-matched terminatorscomprises Compounds 31, 32, 33 and 34.